490 OF SECRETION AND EXCRETION. 



acid and myosin : the former by its combustion yields muscular force, the 

 latter is returned to the circulation to become again the carrier of a fresh 

 portion of glycogen. That this is its destination, he thinks is supported 

 by the fact that muscle naturally contains a not inconsiderable amount of 

 glycogen, as well as by the circumstance that this disappears or is greatly 

 reduced when this tissue is brought into action ; l and, lastly, it is in harmony 

 with the fact that glycogen is abundant in most of the tissues of the embryo 

 in which but little muscular energy is expended. 2 Gaetgheus 3 from experi- 

 ments with phosphorus on dogs, in which large quantities of fat are formed 

 in the Liver, rising sometimes to 11 per cent., apparently from the metamor- 

 phosis of albumen, observes that there is no increase in the amount of glycogen, 

 and is consequently opposed to this view. 4 Taking, however, such informa- 

 tion as we at present possess into consideration, we seem entitled to conclude 

 that the Liver exerts a twofold action on the blood which is traversing its 

 capillaries an assimilative and a depurative. By its operation as an assim- 

 ilating organ it helps to prepare histogenetic material for conversion into 

 blood and solid tissue, in the course of which it is capable of producing and 

 of stormy up amylaceous and oleaginous material in its cells, both of which 

 are capable of being called upon for the maintenance of muscular force and 

 of animal heat; whilst by its depurative action it frees the blood from the 

 protein compounds which are destined to undergo retrograde metamorphosis, 

 as being either superfluous or effete. A portion of these is again, in all proba- 

 bility, applied to the production of amyloid substance and fat; whilst the 

 remainder, containing the nitrogen and sulphur, though a waste of product, is 

 in the form of the bile made subservient to digestion, and the introduction 

 of fresh material into the blood before its final discharge from the body. 



3. The Kidneys. Secretion of Urine. 



402. The Kidneys cannot be regarded as inferior in importance to the 

 Liver, when considered merely as Excreting organs ; but their function only 

 consists in separating from the blood certain effete substances which are to 

 be thrown off from it, and has no direct connection with any of the nutritive 

 operations concerned in the introduction of aliment into the system. The 

 following are the points in the minute structure of these organs, which are 

 of most importance in their Physiological relations. 5 Their glandular and 

 vascular elements. are imbedded in a stroma composed of interlacing fibres 

 (Fig. 176, d d~) ; this is more abundant in the medullary than in the cortical 

 substance ; but at the surface of the gland it is condensed into a contin- 

 uous membrane, which is loosely connected with the proper capsule. The 

 distinction between the cortical and the medullary part of the Kidney essen- 

 tially consists in this, that the former is by far the most vascular, and the 



1 See Wundt, Physiologic, 1873, p. 348. 



2 See Weiss, Wien. Akad. Ber., Ixiv, Heft. 2; also Flint, Physiology, vol. iii, p. 

 315; Lusk, New York Med. Journ., July, 1870; Tyson, Introductory Let-tare de- 

 livered at Pennsylvania College, Nov. 7th, 1870; Senator, Centralblatt, 1871, p. 623. 



3 Centralblatt, 1871, p. 623. 4 See Huppert, Centralblatt, 1869, p. 349. 



5 See especially Mr. Bowman's Memoir in the Philosophical Transactions, 1842; 

 also Goodsir in "Edinb. Monthly Journal, 1842; Gerlach, Bidder, and Kolliker in 

 Miiller's Archiv, 1845; Toynbee in Med.-Chir. Trans., 1840; Johnson in Cyclop, of 

 Anat. and Phys., art. Hen.; Gairdner in Edinb. Monthly Journal, 1848; Freriehs, 

 Die Bright'sche Nierenkrankheit und deren Behandlung, 1851 ; and Kolliker, Mikros- 

 kopische Anatomic, and Man. of Hum. Histol. (Sydenham Soc.); Micros. Anat. 

 1860; Isaacs, Trans. N. Y. Acad. of Med., vol. i, 1857; Henle, Gottincen Abhand- 

 lungen, 1802; and Handbuch der Anatomic, Bd. ii, 1866; Hiifner, Zur vergleieh 

 Anat. u. Phys. d. Ilarncanalchen, Leipzig, 1866 ; Ludvvig, Art. Kidney, in Strieker's 

 Hum. and Comp. Histology, Syd. Soc. Transl., vol. ii, 1872, pp. 83-10'J; Froy's His- 

 tology, translated by Barker, 1874. 



