318 



COMPARATIVE PHYSIOLOGY. 



the tissues, but whether this is used in the manufacture of 

 taurocholic acid or whether the latter is made entirely anew, 

 and possibly by a method in which taurin never appears as 

 such, is an open question. It is highly probable that a portion 

 of the bUe poured into the intestine is absorbed either as such 

 or after partial decomposition, the products to be used in 



some way in the econo- 

 my and presumably in 

 the construction of bile 

 by the liver. There are 

 many facts, including 

 some pathological phe- 

 nomena, that point 

 clearly to the formation 

 of the pigments of bUe 

 from haemoglobin in 

 some of its stages of de- 

 generation. 



Pathological.— When 

 the liver fails to act, 

 either from derange- 

 ment of its cells prima- 

 rily or owing to obstruc- 

 tion to the outflow of 

 bile leading to reabsorp- 

 tion by the liver, bile acids and bile pigments appear in the 

 urine or may stain the tissues, indicating their presence in ex- 

 cess in the blood. 



This action of one gland (kidneys) for another is highly 

 suggestive, and especially important to bear in mind in medical 

 practice, both in treatment and prognosis. The chances of re- 

 covery when only one excreting gland is diseased are much 

 greater evidently than when several are involved. Such facts 

 as we have cited show, moreover, that there are certain common 

 fundamental principles underlying secretion everywhere — a 

 statement which will be soon more fully illustrated. 



• Fig. 359. —Portion of transverse section of hepatic 

 lobule of rabbit magnified 400 diameters (KOUi- 

 ker). 6,|6, 6, capillary blood-Tessels; g, g, g, cap- 

 illary bile-ducts; I, I, l, liver-cells. 



THE NATURE OP THE ACT OF SECRETION. 



We are now about to consider some investigations, more 

 particularly their results, which are of extraordinary interest. 

 The secreting cells of the salivary, the pancreatic glands, 



