148 



PHYSIOLOGY OF FARM ANIMALS 



[CH. 



between the thyroids and parathyroids has already been remarked 

 on, and the inter-relation of the ductless glands and the 

 sexual organs will be toiiched upon in the succeeding chapters. 

 Whether or not there is any true compensating mechanism 

 between internally secreting organs of various kinds is a very 

 open question, but it is abundantly clear that such relation 

 exists between organs of the same kind. Thus, removal of one 

 suprarenal may be followed by compensatory hypertrophy of 













Fig. 72. Section through spleen showing Malpighian 

 corj)uscles (from Schaferj. 



the other (just as happens in the case of the kidneys), and often 

 after extirpation of the main internally secreting organs of a 

 particular kind (e.g. the thyroids) accessory glands may hj^per- 

 trophy and assume the functions of the glands removed. 



In addition to the ductless glands described above there are 

 certain others which so far as known do not elaborate hormones. 

 Of these the most noteworthy are the spleen and the thymus. 



The Spleen. This organ is enclosed within a capsule which 



