36 ANATOMY 



adrenalectomy leads to the same fatal outcome as in the cat or 

 dog. The glands, being relatively large in the cat and dog, 

 may be easily extirpated without leaving bits of tissue which 

 might hypertrophy. In the mouse or rat, on the other hand, 

 the glands being extremely small and friable, it is easy to 

 detach bits of cortical tissue which, although microscopic, 

 suffice to permit regeneration and survival of the animal. 

 In the rabbit, the right adrenal is often so firmly attached to 

 the vena cava as to render its complete extirpation difficult. 



That the frequency of occurrence of accessory adrenals in the 

 rat or mouse is not based on sound grounds but is explicable 

 on the basis of the above interpretation has been demonstrated 

 by many recent workers. The relative infrequency of these 

 accessories in the rat and mouse can also be definitely proven 

 by serially sectioning the adrenal sites including all the sur- 

 rounding connective tissue. 385 When this is done one finds 

 surprisingly few accessory bodies and these are always present 

 in the connective tissue investing the adrenals. They are not 

 scattered throughout the abdominal cavity as was formerly 

 believed. 



Some authors have claimed that certain breeds of rats con- 

 tain diffusely scattered accessory bodies and hence survive 

 adrenalectomy while others being devoid of such accessory 

 tissue do not survive the operation. These authors, however, 

 give no specific identification of these breeds but apparently 

 arbitrarily differentiate certain animals as being of a different 

 strain on the basis of their survival following adrenalectomy. 

 All recognized strains of the common rat {Mus Norvegicus) 

 have been subjected to adrenalectomy in the author's lab- 

 oratory without encountering the hypothetical accessory- 

 endowed strain assumed by certain authors. 



The true accessory cortical tissue occurs usually only in the 

 near vicinity of the main glands. The accessory tissue which 

 is found in various parts of the abdominal cavity at some dis- 

 tance from the main glands is usually a part of the androgenic 

 tissue and shall be described in Chapter IV. 



