PHYSIOLOGY OF THE INVERTEBRATA. 87 



digested or dissolved — only leaving the horny integument 

 (hyalin). This integument did not appear to be formed of 

 chitin, for it was rapidly attacked by a boiling solution of 

 potash. 



The Annelida. 



(a) The Hirvdinea. For this purpose Fredericq cut into 

 pieces twelve horse-leeches (ITcemophsis vorax), and from these 

 pieces he prepared two extracts, one acid and the other alka- 

 line. Fibrin was digested (in twelve hours) in the alkaline 

 extract, but was unaltered in the acid extract. 



The author of ,the present volume has obtained similar 

 results with Hirudo medicinalis. Digestion, therefore, in the 

 Jlirudinea is somewhat similar to the pancreatic digestion in 

 the Vertebrata. 



(h) The Oligochmta. In this order, represented by Lumbrims 

 tcrrestris, the digestive system (Fig. 24) is more highly de- 



FiG. 24. — Diagram of Anterior Portion of Alimentary Canal 



OF LUMBRICUS, 



a = mouth. 6 = salivary glands (?). c = oesophagus, d = pharynx, 

 e = calciferous glands. / = crop, g = gizzard, h = intestine. 



veloped than in any other animal already alladed to in the 

 present chapter. 



If the head or anterior portion of Zumbrims (as far as the 

 sixth segment) is severed from the body, and that part of 

 the alimentary canal which it contains is dissected out of the 

 head, and is placed on starch, it will be converted into 

 glucose, but it has no action on fibrin. From this there is 

 no doubt that the saliva is poured into the pharynx. This 

 secretion bathes the food (which is of a mixed nature) 

 during its passage through the oesophagus. Attached to 



