208 



starchy substance, which is derived from the food and 

 transformed into glycogen and supplied (in the form of 

 sugar) to the blood as required ; (2) the conversion of 

 nitrogenous wastes into urea or uric acid for excretion 

 through the kidneys ; and (3) the secretion of bile for 

 emulsifying fats. There is generally a bile reservoir, the 

 gall-bladder, associated with the bile-duct. The pancreas 

 (sweetbread) arises from the region of the bile-duct ; it 

 secretes pancreatic juice which contains the ferments for 

 completing the process of digestion. 



The intestine (digestive and absorptive) is usually long, 

 and more or less looped and convoluted ; its principal 

 portions are the small intestine (duodenum, jejunum and 

 ileum) and the large intestine (caecum with vermiform 

 appendix, colon, and faecal rectum). In some Fishes (e.g., 

 Elasmobranchs and Dipnoi) the large intestine (colon) 

 has an internal corkscrew-like fold, the spiral valve, and 

 thereby the absorptive surface is greatly increased. This 

 fold is the result of the twisting growth of the intestine 

 within its outer peritoneal coat. In Amphibians (e.g., Frog) 

 the rectum has a ventral outgrowth, which functions as 

 a urinary bladder ; in the embryos of higher Craniates 

 this becomes the allantois (see pages 213, 249, 260). 



Name the Ductless Glands, and stale what, you, knou< about 

 their Functions and Development. 



1. The lymphatic "glands." (See page 211.) 



2. The spleen, chiefly a blood-making organ, in which 

 blood corpuscles are formed. It is situated near the pyloric 

 end of the stomach, frequently beside the pancreas, and is 

 developed from " a condensation of mesenchyme of the 

 gut-wall." 



3. The thymus. (Sc.e previous answer.) 



4. The thyroid, the secretion of which has an important 

 influence on the general metabolism, especially in relation 

 to the nervous system and the growth of sub-cutaneous 

 tissue. Atrophy or disease of the thyroid in children 

 produces that form of idiocy called cretinism, and in adults 

 is the cause of myxoedema. Hypertrophy of the thyroid 

 results in goitre. (See previous answer.) 



5. The supra-renal or adrenal bodies, which are situated 

 on or beside the kidneys, secrete a substance essential 

 for muscle tone. 



0. The pituitary body. (,SW page. 201.) 



NOTE. 1, 2 and 3 are not " glands " in the strict sense. 



