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The anatomy of the frog

Chapter 88: NOTE BY THE TRANSLATOR.
By Alexander Ecker
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About This Book

The manual offers a systematic, descriptive account of frog anatomy, organized into sections treating the skeleton and joints; musculature; nervous system; circulatory and lymphatic systems including the heart; the alimentary tract with liver, spleen, and peritoneum; respiratory organs and associated glands; the urinary and reproductive organs with accessory structures; and the skin and sense organs. It incorporates microscopic and vascular detail, numerous illustrations and plates, and bibliographic references, with revisions and annotations to update anatomical descriptions and figures. Emphasis is on practical morphological description rather than comparative, developmental, or purely histological analysis.

NOTE BY THE TRANSLATOR.

Reference has already been made to the views of Messrs. Melland and Marshall on the structure of muscle-fibres. The opinion that the striation of voluntary muscle is wholly or in part due to the presence of a regularly arranged network was previously published by Retzius, Bremer, and others. The authors referred to have now for the first time shown the importance of this network in all vertebrate muscular tissues, whether voluntary or involuntary.

Mr. Marshall gives the following summary of the result of his researches, which the Translator has confirmed by his own observations:‍—

1. In all muscles which have to perform rapid and frequent movements, a certain portion of the muscle is differentiated to perform the function of contraction, and this portion takes on the form of a very regular and highly modified intracellular network.

2. This network, by its regular arrangement, gives rise to certain optical effects which cause the peculiar appearances of striped muscle.

3. The contraction of the striped muscle-fibre is probably caused by the active contraction of the longitudinal fibrils of the intracellular network; the transverse networks appear to be passively elastic, and by their elastic rebound cause the muscle to rapidly resume its relaxed condition when the longitudinal fibrils have ceased to contract; they are possibly also paths for the nervous impulse.

4. In some cases where muscle has been hitherto described as striped, but gives no appearance of the network on treatment with the gold and other methods, the apparent striation is due to optical effects caused by a corrugated outline in the fibre.

5. In muscles which do not perform rapid movements, but whose contraction is comparatively slow and peristaltic in nature, this peculiar network is not developed. In most if not all of the unstriped muscles of invertebrates there does not appear to be an intracellular network present in any form, but in the unstriped muscle of vertebrates there are longitudinal fibres only; these possibly represent a form of network intermediate between the typical irregular intracellular network of other cells and the highly modified network of striped muscle.

6. The cardiac muscle-cells contain a network similar to that of ordinary striped muscle.

DESCRIPTION OF THE FIGURES ON PLATE II.

Fig. 180 (p. 278).

I. Preparation of the mucous membrane of the dorsal surface of the mouth and oesophagus to show the vascular supply. Arteries red, veins blue; after Schöbl.
II. Small portion of the above to show the dilatations on the capillaries; after Schöbl.

Fig. 187 (p. 285).

Transverse section through the mucous membrane of the fundus of the stomach of Rana esculenta. Alcohol preparation, doubly stained with carmine and anilin blue. After Biedermann. (Oc. II, Syst. 7, Hartnack.)

Fig. 196 (p. 298).

I. Partial injection of the liver from the portal vein (blue): Rana esculenta.—G. H.
II. Partial injection of the liver from the hepatic vein (red): Rana esculenta.—G. H.
III. Complete injection of the liver from the hepatic artery (red) and from the portal vein (blue): Rana esculenta.—G. H.
A Portal (interlobular) veins and their branches.
B Hepatic (intralobular) veins and their branches.
C Hepatic arteries and their branches.

Fig. 208 (p. 318).

Two sections from the lung of Rana temporaria; stained with borax-carmine.—G. H.

I. The lung dilated (Hartnack, Oc. I, Syst. 3).
II. The lung contracted (Hartnack, Oc. I, Syst. 7).
A Band of muscle cut transversely.
B Band of muscle cut longitudinally.
C Muscular layer of surface.

Fig. 217 (p. 334).

Portions of two transverse vertical sections through the kidney.—G. H.

I. Kidney of Rana esculenta, partial injection of the uriniferous tubes with silver nitrate (Hartnack, Oc. I. Syst. 7).
II. Kidney of Rana temporaria, stained with borax-carmine (Hartnack, Oc. I, Syst. 7).

Fig. 219 (p. 337).

Two portions from a gold preparation of the kidney of Rana esculenta.—G. H.

I. Showing the tendency to split into lobules.
II. Nerve-fibres accompanying the blood vessels.
a Blood-vessels.   b Nerves.