8g PHYSIOLOGY OF THE INVERTEBRATA. 



the sides of the posterior end of the oesophagus are three 

 pairs of calciferous glands. These glands secrete a sub- 

 stance extremely rich in calcium carbonate. The function o^ 

 these glands in secreting calcium carbonate is to neutralise 

 the vegetable acids o.f the food, for the digestive fluid of 

 Zuviiricus is inactive unless alkaline. The food and fluids in 

 the crop of the earthworm are always alkaline. In the crop 

 the food matter is stored before it passes into the gizzard, 

 whose powerful muscular walls and thick chitinous lining 

 crush any food-stuffs that require mastication or grinding. 

 The posterior portion of the gizzard has thinner walls, and 

 leads into the long glandular intestine, which is lined with 

 columnar cells. The intestine is almost enveloped in a 

 yellowish glandular tissue — the so-called liver. This organ is 

 essentially pancreatic in function.* 



There is no doubt that the principal digestive fluid of 

 worms is of the same nature as the pancreatic juice of the 

 Vertehrata. Dr. Leon Predericq (Archives de Zoologie Expiri' 

 mentale, vol. vii. p. 394) proved this in the following 

 manner : — 



A large quantity of worms, chopped into small pieces, are 

 treated with strong alcohol. The alcohol is left to act for 

 many hours ; and then decanted. The alcoholic extract is 

 used in the examination for biliary acids. The insoluble- 

 residue is pressed between several folds of filter paper, dried 

 in air, and finally pulverised in a mortar. The pulverised 

 residue is divided into several parts, the object being tc 

 prepare several aqueous extracts (neutral, alkaline, and acid). 

 The dilute acid solutions used in preparing the acid extracts 

 are made from hydrochloric acid and water (the degrees of 

 concentration being from six to twelve cc. of HCl per litre 

 of water). The divided residue (previously alluded to) 

 is allowed to macerate in the fluids for twenty-four hours ; 

 and then filtered. The filtered liquids are placed in separate 

 test-tubes in each of which a small piece of fibrin has beea 



* Dr. A. B. Griffiths' paper in Proc. Boxj. Soc. Edinh., vol. 14, p. 237. 



