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CHAPTER XIII. 



THE VASCULAR GLANDS; OR GLANDS WITHOUT DUCTS. 



THE materials separated from the blood by the ordinary 

 process of secretion by glands, are always discharged from 

 the organ in which they are formed, and either straight- 

 way expelled from the body, or if they are again received 

 into the blood, it is only after they have been altered from 

 their original condition, as in the cases of the saliva and 

 bile. There appears, however, to be a modification of the 

 process of secretion, in which certain materials are ab- 

 stracted from the blood, undergo some change, and are 

 added to the lymph or restored to the blood, without being 

 previously discharged from the secreting organ, or made 

 use of for any secondary purpose. The bodies in which 

 this modified form of secretion takes place, are usually 

 described as vascular glands, or glands without ducts, and 

 include the spleen, the thymus and thyroid glands, the 

 supra-renal capsules, and, according to (Esterlin and 

 Ecker and Gull, the pineal gland and pituitary body; 

 possibly, also the tonsils. 



The solitary and agminate glands of the intestine 

 (p. 302), and lymph-glands in general also closely resem- 

 ble them; indeed, both in structure and function, the 

 vascular glands bear a close relation, on the one hand, 

 to the true secreting glands, and on the other, to the 

 lymphatic glands. 



The evidence in favour of the view that these organs 

 exercise a function analogous to that of secreting glands, 

 has been chiefly obtained from investigations into their 

 structure, which have shown that most of the glands with- 

 out ducts contain the same essential structures as the 

 secreting glands, except the ducts. They are mainly com- 



