126. The student should bear in mind that these terms are employed simply as a matter of convenience in description; all the parts, though differently named, form a continuous whole.

127. The apertures do not exist in the fœtus, and are sometimes absent in the adult subject. Some of them may be produced in dissection by the necessary disturbance of the parts. Clinicians state that a serous exudate formed in one pleural sac usually passes through to the other side in the horse.

128. A correct idea of the natural form and size of the lung cannot be obtained from a specimen in this state. The lungs should be hardened in situ for this purpose.

129. Some authors consider each lung to be divided into anterior and posterior lobes by the cardiac notch, so that the right lung would have three lobes and the left lung two lobes.

130. In fœtal lung the lobulation is much more distinct. Pigmentation of the lung is sometimes seen in horses, and in such cases the pigment is deposited mainly in the interlobular tissue, thus mapping out the lobules.

131. It must not be inferred from the necessarily brief account here given that the two sets of vessels are quite distinct. On the contrary, competent observers state that numerous small branches of the bronchial arteries anastomose with pulmonary vessels. Part of the blood conveyed to the lungs by the bronchial arteries is returned by the pulmonary veins. In the horse bronchial veins are absent or inconstant.

132. The cervical part of the gland is very variable. The thoracic lobe of one side may have no cervical continuation; the other lobe may then give off a single prolongation which bifurcates. The thoracic part in the new-born foal occupies most of the space which is later taken up by the apices of the lungs. Its two lobes are in contact, and its deep surface is molded on the anterior part of the pericardium and the large vessels.

133. It is therefore often termed the precardiac lobe.

134. The arrangement here is one of the most striking features of the pig’s larynx. The short, thick middle hyo-epiglottic ligament and the anterior part of the thyro-hyoid membrane are inelastic, while the posterior part of the membrane is thin and elastic and allows the epiglottis to be separated by a considerable interval from the thyroid cartilage. Moreover, the borders of the epiglottis are connected with the thyroid cornua of the hyoid bone by lateral hyo-epiglottic ligaments.

135. The kidneys are soft, plastic organs, and hence an accurate knowledge of their form can be gained only from a study of specimens which have been hardened in situ. The description here given is based on this method. For this purpose subjects should be hardened in the standing position to avoid artefacts.

136. The most instructive sections are those made in the horizontal and transverse planes, through the pelvis in each case.

137. The fœtal kidney is divided by furrows into a number of polygonal areas, each of which is the base of a pyramidal lobe or renculus. These furrows usually disappear before or soon after birth in the foal, although traces of them are sometimes seen in the adult.

138. In the kidney of the horse the renal columns dip in between the pyramids very superficially as compared with the arrangement in the human kidney. Breuer states that the pyramids are 40 to 64 in number, and are arranged in four rows. Only the middle ones are distinct.

139. The crest is the result of fusion of the papillæ or apices of the pyramids in the embryo.

140. This is commonly termed the fundus by veterinarians, but is not the homologue of the fundus of the human bladder.

141. This would correspond to the fundus vesicæ of man.

142. From the standpoint of comparative anatomy the term “adrenal” seems decidedly preferable to “suprarenal.”

143. This is a remnant of the gubernaculum testis of the fœtus.

144. The tunica vaginalis is not a part of the scrotum in the strict or narrow sense of that term, but is included here on practical grounds.

145. Sometimes one vesicula or both are very large in the gelding. The writer has seen four cases in the dissecting room, three of which were bilateral, the other unilateral. The vesicula resembled the urinary bladder in appearance and contained about a quart of thick, amber-colored secretion.

146. It has been customary to divide the pelvic part of the urethra into prostatic and membranous parts. These terms apply well in human anatomy, but have no special value in comparative anatomy. In the horse a prostatic part hardly exists, unless we assume that it and the neck of the bladder together are only about an inch in length. There is no membranous part in the sense in which that term is used in regard to man.

147. The statement often made that it acts as a sphincter of the bladder is a hypothesis of doubtful plausibility. In material hardened in situ, in which the internal urethral orifice is tightly closed, the urethral muscle apparently takes no part in the closure.

148. This is clinically important, since enlargement of the prostate may interfere with micturition.

149. These terms apply properly only when the adjacent viscera are removed and the ovaries are actually “suspended” by the broad ligaments. When the ovary is in its natural position, the surfaces are dorsal and ventral, the former corresponding to the “external” surface if the free border is directed outward, to the “internal” if the free edge is medial.

150. The Fallopian tubes may be regarded, both in structure and morphology, as prolongations of the uterus (McMurrich).

151. The arrangement is the only exception to the general rule that the serous cavities are closed. In this case the mucous membrane of the fimbriated extremity is continuous with the adjacent peritoneum, a persistence of the embryonic relations of the Müllerian duct.

152. In formalin-hardened subjects there is frequently a pronounced ring-like constriction at the beginning of the vulva.

153. The term vulva is used here in the sense in which it is understood generally by English and French veterinarians. In the German works it is applied only to the labia and other structures around the external orifice of the urogenital sinus, while the sinus itself is termed the vestibule of the vagina (Vestibulum vaginæ).

154. Lesbre states that the cornua may attain a length of 45 to 50 cm.

155. The pericardium is described before the heart since it must be examined first in the laboratory.

156. This is termed the tubercle of Lower in human anatomy and the tuberculum intervenosum by German veterinary anatomists.

157. These vessels will be described later in their systematic order.

158. The relation to the guttural pouch is not constant. In some cases—especially when the head and neck are extended—the artery lies behind the pouch. The backward extension of the latter is variable.

159. By some authors the term facial is applied to the artery only after it turns around the lower border of the jaw.

160. The artery is conveniently placed at its inflection for taking the pulse, since it is superficial and lies directly on the bone.

161. This vessel appears to represent both the supraorbital and frontal of man.

162. The term axillary is often applied to the artery from the first rib to the point of origin of the subscapular branch.

163. The pulse can be taken where the artery lies on the lateral ligament, since the pectoral muscle is thin here.

164. This vessel is also termed the A. metacarpea volaris superficialis or the palmar metacarpal artery.

165. In the great majority of subjects this vessel and some of its branches are the seat of more or less extensive verminous aneurysm, produced by the Sclerostomum armatum. In the author’s experience an entirely normal specimen is quite exceptional in adult horses.

166. The left branch is a descriptive convention rather than a reality, since the arteries of the small intestines spring from the mesenteric trunk either directly or by short common stems with an adjacent vessel.

167. The obliteration in the adult extends a variable distance from the vesical end toward the origin, but usually involves only a small part.

168. Most of the veins are depicted in the illustrations of the section on the arteries, to which reference is to be made.

169. Chauveau says “the bronchial veins, which ramify on the bronchi like the arteries of which they are satellites, open into the great coronary vein very near its mouth, after having united to form a single vessel, which sometimes opens directly into the atrium.” Ellenberger and Baum state that the bronchial and œsophageal veins open into the vena azygos separately or by a common trunk. Martin describes a short broncho-œsophageal trunk, but the vein which he figures as the bronchial does not come from the lungs, but is a small mediastinal vessel. The author finds such a vessel entering the terminal part of the œsophageal vein, but no distinct bronchial vein in the horse.

170. M’Fadyean records a case in which the vein lay on the deep face of the omo-hyoideus with the carotid artery.

171. The venous angle formed by this junction indicates the position of the thyroid gland.

172. These are termed by Chauveau and M’Fadyean the subsphenoidal confluents.

173. The place and mode of termination is quite variable. It may disappear from the surface of the thigh at any point above the distal third. In some cases it passes through the anterior part of the gracilis instead of dipping in between that muscle and the sartorius.

174. This often joins the posterior femoral or the popliteal vein.

175. The term chyle is often applied to the lymph carried by the efferent vessels of the intestine when it contains products of digestion, and these vessels may be designated as lacteals or chyle vessels.

176. The lymph vessels of these organs appear to vary considerably in their mode of termination, and the arrangement needs further study. Some ducts from the stomach, liver, and spleen open directly into the cistern.

177. Abscess here can be reached readily by an incision between the vein and the omo-hyoideus.

178. It is, of course, only the pericardium which comes in contact with the wall, but it is customary as a matter of convenience to speak of the relation of the heart as though it were direct.

179. Only the most important differential features of the arrangement of the vessels as compared with those of the horse will be considered.

180. The homologies of the vessels of the lower parts of the limbs are still uncertain. The account given here is mainly based on the views of Sussdorf and Baum.

181. It is difficult to make the arrangement of these vessels clear in a brief textual description, but a reference to the schematic figure will explain the main facts.

182. Most of the differences in the veins of the ox are correlated with those of the arteries of which they are satellites and will not be described. The account here given consists chiefly of those differential features which could not be deduced from a knowledge of the arteries.

183. The upper series is continuous with the posterior mediastinal (œsophageal) glands and the lower or tracheal glands with the bronchial. Hence we might well designate the mediastinal glands as œsophageal (anterior and posterior) and tracheo-bronchial.

184. When enlarged, as is often the case in tuberculosis, this gland frequently causes difficulty in swallowing and in rumination and produces chronic or recurrent bloating.

185. The relative weight is subject to wide variation. It is large in hunting dogs and such as are trained for speed or worked.

186. Limitations of space and the purpose of this work preclude consideration of the finer structure of the nervous system, for which ample literature is available.

187. The description given here is intended to present the chief facts in regard to the brain as they may be studied in the dissecting room. The vessels and membranes which must be examined first have been described.

188. Unless care is used in removing the brain the infundibulum is likely to be torn and the pituitary body left in the cranium. In this case there is a small opening which communicates with the third ventricle.

189. The fossa corresponds in position to the locus perforatus anticus of the human brain, but is not pierced by numerous openings for vessels in the horse.

190. The decussation varies superficially in different specimens. In some there is a distinct superficial crossing of fibers so that the median fissure is practically effaced at this point.

191. In the new nomenclature the term lamina quadrigemina is applied to the dorsal mass of the mid-brain, and the four eminences which it bears are the corpora quadrigemina.

192. In man a distinct superior brachium connects the superior pair with the lateral geniculate body, but in the domesticated animals the union with the optic thalamus is too direct to allow of any definite arm being recognized.

193. On a strictly embryological basis the optic part of the hypothalamus, comprising the anterior part of the third ventricle and the structures associated with it, belong to the telencephalon, but will be considered here as a matter of convenience.

194. This backward projection of the thalamus is equivalent to the pulvinar and lateral geniculate body of man, which are not superficially divided in the domestic animals.

195. In order to study the configuration of the hemisphere it should be separated from its fellow by median section and from the brain stem by cutting across the mid-brain. Material for this purpose should be hardened in situ.

196. Termed by Lesbre the parietal fissure and by M’Fadyean the great oblique fissure.

197. Just above this point is a lobe which is homologous with the insula of man. When the overhanging gyri which partly conceal it—forming the operculum—are removed, there are disclosed several short, deeply placed gyri (Gyri breves).

198. By some authors this is regarded as the homologue of the cruciate fissure of the dog, but it seems likely that the latter is represented by a short and inconstant sulcus situated further forward.

199. From the morphological point of view other structures should be included, but in descriptive anatomy it is usual to limit the application of the term to the parts enumerated above.

200. It is generally believed that these constitute an olfactory path.

201. It is hardly possible to get an accurate idea of the shape of the ventricle except by studying a cast of it. The size of the ventricles varies in different subjects, and it is not rare to find more or less disparity between the two ventricles of the same brain.

202. The term arose from the striated appearance of the mass in sections cut in certain planes, the gray matter being cut up into strands by tracts of white fibers.

203. Although this nerve springs directly from the ganglion, it contains motor as well as sensory fibers.

204. This ganglion appears to be equivalent to the jugular or superior and petrous ganglia of man.

205. In some cases the left vagus passes back below the junction of the jugular veins and the termination of the left brachial vein. It then runs backward and somewhat dorsally across the left face of the anterior vena cava to reach its usual position.

206. The nerve lies here about a finger’s breadth above the thyroid gland. If, however, the gland is enlarged it may come in contact with the nerve. The same is true in regard to the relation to the anterior cervical lymph glands.

207. In order to examine the plexus and the origins of its chief branches conveniently and with as little disturbance of relation as possible, the subject should be suspended in imitation of the natural position and the fore limb abducted as much as is necessary.

208. Morphologically the last-named muscle belongs to the extensor group. In man and in the dog and many other animals it is an extensor in function.

209. In veterinary works these are frequently termed plantar nerves, which is an unfortunate misnomer. The writer inclines to the use of the old term metacarpal or common digital to designate the nerves as far as their divisions, and the term digital beyond this.

210. The special statements of this description refer to the system of the horse. A few important differential features will be mentioned in the account of the nervous system of the other animals.

211. The right and left plexuses communicate with each other, so that both lungs receive fibers from both vagi.

212. It has been customary to designate these in veterinary works as the semilunar or cœliac ganglia, but in the horse they evidently include the anterior mesenteric ganglia as well.

213. A good preparation of the ganglia in the horse is often difficult to obtain on account of aneurysm of the artery and the formation of a quantity of connective tissue about it.

214. Only the most salient differences as compared with the horse will be mentioned.

215. The origin of the lacrimal nerve is such that Ellenberger-Baum and Martin describe it as a branch of the maxillary nerve.

216. Lesbre terms this the tracheo-œsophageal branch, and considers that it must be regarded as an accessory or internal recurrent nerve.

217. This belongs to the upper eyelid, but is described here on account of its position.

218. According to Piersol the system of spaces and canaliculi in the substantia propria is completely filled by the cells and their processes, upon which the nutrition of the cornea largely depends. The lamina elastica anterior, formerly described as a distinct layer between the corneal epithelium and the substantia propria, does not exist as such, but there is a condensation of the superficial part, of the latter, which Rollett termed the anterior limiting layer; it is not elastic.

219. In albinos the pigment is absent here, as elsewhere, and the iris is pinkish in color.

220. For the minute structure of the retina reference must be made to histological works.

221. Ellenberger and Baum regard this as the homologue of the transversus and obliquus auriculæ of man.

222. There is, strictly speaking, no osseous part of the tube such as occurs in man. In the horse the cartilage extends to the tympanic orifice.

223. For the finer structure reference is to be made to the histological literature.

224. This muscle has been described in the Myology.

225. To prevent a possible misapprehension, it may be stated that the epidermis primarily molds the corium, and that the glands and hair-follicles are invaginations of the epidermis.

226. The hoof may be loosened and removed intact by allowing the foot to macerate or by boiling it.

227. The term foot is used here in the popular sense, i. e., to designate the hoof and the structures inclosed within it.

228. The wide groove at the heels, however, contains chiefly the matrix of the periople.

229. The lower punctum lacrimale is frequently absent and the corresponding duct therefore blind. There is often a duct or its remnant which opens below the inferior turbinal fold, but is not connected behind with the functional duct.