486 OF SECRETION AND EXCRETION. 



ill these instances it appears to have little tendency to become transformed 

 into sugar. The " corpora amylacea " of Virchow, observed as pathological 

 formations in the kidney, spleen, and other organs, and at one time consid- 

 ered to be identical with amyloid substance, differ from it essentially in con- 

 taining nitrogen. 1 



398. After the presence of an amyloid material was shown to be constant 

 in the liver, and to precede the formation of sugar, it was supposed that 

 some ferment was requisite by which, either in the hepatic cells themselves, 

 or after the absorption of the starch into the blood, its conversion into sugar 

 could be rapidly effected. Many efforts were made to ascertain the source 

 of this ferment; and the spleen, thymus, thyroid, suprarenal, salivary, and 

 pancreatic glands were successively extirpated by Schiff, 2 without, however, 

 his being able to determine whether any of them were instrumental in its 

 formation. Bernard, 3 Hensen, and Cohnheim, 4 maintain that the ferment is 

 thrown down with the amyloid substance on the addition of alcohol to the 

 cold aqueous infusion of the liver ; that it is rendered inoperative by boiling ; 

 and finally, that it is contained in ordinary arterial blood, and in the blood 

 of the vena portse, the addition of such blood to a solution of glycogen effect- 

 ing its conversion into sugar. The necessity for the existence of this ferment 

 has been rendered doubtful by the investigations of Dr. Pavy, 5 whose experi- 

 ments have led him to the following conclusions: 1. That the liver normally 

 and during life, whatever may have been the nature of the food, contains 

 little or no sugar, but a considerable proportion of amyloid substance ; since 

 if it be removed from the body instantly after death, and subjected to the 

 action of caustic or carbonated potash or soda, or of extreme cold, no sac- 

 charine reaction can be obtained, though the presence of the amyloid sub- 

 stance can easily be shown. 2. That, during life, there is under ordinary 

 circumstances very little difference in the amount of sugar contained in dif- 

 ferent specimens of blood, whether withdrawn from the systemic arteries or 

 veins, the portal vein, or (by means of a catheter introduced through the 

 jugular vein) 6 from the right auricle ; the latter of course containing a large 

 proportion of hepatic venous blood ; the quantity of sugar present in all in- 

 stances being extremely small, and varying from T f ( 2 D ths to 7ooo^ ns f a grain 

 per cent. 3. That during life, therefore, very little amyloid substance is 

 taken up by the blood in its passage through the liver, as indeed might be 

 anticipated from its low power of dialyzing through animal membranes. 

 On the contrary, after death, and frequently from various disturbing causes 

 during life, such as violent muscular action or embarrassment of the respira- 

 tion, a conversion of the amyloid substance into sugar takes place in the 

 substance of the liver itself, and the sugar so formed then quickly appears in 

 the blood, often to so great an extent as to occasion diabetes. 



399. At an early period of the history of the glycogenic function of the 

 Liver, it was found that the formation of glycogen could be influenced 

 through the nervous system. Bernard, for instance, observed that when the 

 floor of the fourth ventricle between the origin of the Pueumogastric and 

 Auditory nerves (see Fig. 175) was pricked with a needle, 7 so great an in- 



1 See Dr. Pavy's Gulstonian Lectures for 18G3. 



2 Unters. iib. die Zuckerbildung der Lebor, Wurzburg, 1859. 



J Kcvue Sciontif., 1873, Lcct. xviii. See also v. Wittich, Centralblatt, 1873, p. 365. 

 4 Virchow's Archiv, Bd. xxvii, p. 241. 



6 See his work on Diabetes, 18(38. See Hitter, Zeitsehrift f. rat. Mod., Bd. xxiv, p. 

 05; Schiit', Journal dc 1'Anatomie, Robin, 1806; McDonnell, Observations on the 

 Functions of the Liver, 18(!">. 



See on this point also McDonnell, Proceedings of the Royal Irish Society, 1868. 



7 Though not, according to Dock, if the animal has been kept fasting for several 

 days. Ptluger's Archiv, vol. v, 1872, p. 583. 



