PHYSIOLOGY OF THE INVERTEBRATA. loi 



by the rose colour produced in tlie cold by potash and copper 

 sulphate. 



(5) Tannic acid produces a white precipitate with the sec- 

 retion. 



(6) "When a few drops of the secretion of these ducts were 

 examined chemico-microscopically, the following reactions 

 were observed : on running in a solution of iodine (in potas- 

 sium iodide) between the slide and cover-glass, a brown de- 

 posit was obtained ; and on running in concentrated nitric 

 acid, on another slide containing the secretion, yellow xantho- 

 proteic acid was formed. These reactions prove the presence 

 of albumin in the secretion of the organ in question. The 

 presence of albumin was further confirmed by the tests of 

 Palm.* 



(7) The soluble ferment, or enzyme, secreted by the cellular 

 tubes was extracted, although with some difficulty, by the 

 Wittich-Kistiakowsky method. This ferment converts fibrin 

 into leucin and tyrosin. 



(8) The albumins in the secretion and extract are not 

 converted into taurocholic or glycocholic acids, for not the 

 slightest traces of these biliary acids could be detected by the 

 Pettenkofer and other tests. 



(9) The secretion contains approximately four per cent, of 

 solids. The slight residue (solids), which contains some com- 

 bination of sodium, effervesced on the addition of dilute acid. 



(10) No glycogen was found in the secretion or extract. 

 From these investigations, which have been repeated on 



several occasions, the so-called liver of the Araneina is proved 

 to have a similar function to the jDancreas of the Vertebrata. 



The Crustacea. 



(i) The Brachijura. — As a type of this order, the alimentary 

 canal of Carcinus mcenas will be considered in detail. 



This animal is a voracious feeder ; its food consists of 



* ZeitscJtrift fur Analytlsohe Chemie, vol. 24, pt. i. 



