276 THE DUCTLESS GLANDS 



last difference, however, can only be detected in adult animals. 

 In some species, as the rabbit, the internal parathyroid is 

 intimately connected with a " central canal " (post-branchial 

 body) and with the thyroid itself. 



FIG. 79. Human. A drawing, as seen under a simple 

 lens of a portion of the thyroid and a parathyroid 



p. thyr. -\ which is considerably hypertrophied and otherwise 



modified. The specimen is pathological, but there 

 is no record of the patient. The object of this 

 figure is to show that the structure in question 



thyr.- is in reality morphologically and topographically 



a parathyroid. 



p. thyr., parathyroid ; thyr., thryoid. 



In close contact with each of the parathyroids we may 

 find a thymus nodule, and occasionally the central portion 

 of this last is seen to be directly continuous with the tissue 





FIG. 80. A portion of the thyroid and neighbouring parathyroid, with a 

 fairly thick connective-tissue partition ; low power. On the left \\ < 

 see the colloid vesicles of the thyroid ; on the right the parathyroid, which 

 is of(a typical parathyroid structure near the- connective-tissue septum ; 

 but which shows several undoubted colloid vesicles in the left-hand 

 portion of the drawing. 



