414 THE DUCTLESS GLAXDS. 



smaller vessels, so as to be a fine retiform tissue, with 

 abundance of corpuscles, like lymph- corpuscles contained 

 in its meshes ; and the Malpighian corpuscles are but 

 small outgrowths of this cytogenous or cell-bearing con- 

 nective tissue. They are composed of masses of corpuscles, 

 intersected in all parts by a delicate fibrillar tissue, which, 

 though it invests the Malpighian bodies, does not form a 

 complete capsule. Blood-capillaries traverse the Malpi- 

 ghian corpuscles and form a plexus in their interior. The 

 structure of a Malpighian corpuscle of the spleen is, 

 therefore, very similar to that of lymphatic-gland sub- 

 stance (p. 355). 



The general resemblances in structure between certain of 

 the vascular glands and the true glands lead to the supposi- 

 tion that both sets of organs pursue, up to a certain point, 

 a similar course in the discharge of their functions. It 

 is assumed that certain principles in an inferior state of 

 organization are effused from the vessels into the sacculi, 

 and gradually develop into nuclei or cytoblasts, which may 

 be further developed into cells ; that in the growth of these 

 nuclei and cells, the materials derived from the blood are 

 elaborated into a higher condition of organization; and 

 that when liberated by the dissolution of these cells, they 

 pass into the lymphatics, or are again received into the 

 blood, whose aptness for nutrition they contribute to 

 maintain. 



The opinion that the vascular glands thus'serve for the 

 higher organization of the blood, is supported by their 

 being all especially active in the discharge of their functions 

 during foetal life and childhood, when, for the development 

 and growth of the body, the most abundant supply of 

 highly organized blood is necessary. The bulk of the 

 thymus gland, in proportion to that of the body, appears to 

 bear almost a direct proportion to the activity of the body's 



