m6 physiology of THE INVERTEBRATA. 



The chief digestive glands of the Inrertchrato. are the 

 pancreas (the so-called liver) and the salivary glands. There 

 appears to be no organ, from the lowest to the highest 

 Invertebrate animal, corresponding with the Vertebrate liver. 

 Dr. 0. Letourneau, in his La Biologic, says : " Does the 

 IJaticrms exist in the Invertebrates ? This is a question of 

 comparative physiology which still waits for a reply. We do 

 not begin clearly to recognise the pancreas except in fishes, 

 and then only in a rudimentary state." After the recent 

 researches of Krukenberg, Fredericq, Jousset de Bellesme, 

 Plateau, Hoppe-Seyler, as well as those of the author, the 

 problem now requiring solution is the following : — Does a 

 true liver exist in the Invertehrata ? The pancreas appears 

 to be the chief digestive organ of the earlier forms of animal 

 life. 



On the other hand, some biologists look upon the Verte- 

 brate liver, pancreas, and salivary glands as differentiated 

 bodies of an original pancreas of the Invertehrata. But have 

 not many forms of the lower animals similar salivary glands 

 to those found in the Vertchrata. ?- And is not the so-called 

 liver of the Invertehrata a true pancreas, capable of producing 

 the same chemical and physiological reactions as the pancreas 

 of higher forms ? 



