38 ANATOMY 



ciate this temporary appearance of a new tissue in the gland 

 has led to certain of the discrepancies found in the litera- 

 ture. 319 - 671 



As Kolmer 362 has indicated, the microscopic appearance of 

 the adrenals of every animal has certain distinctive properties 

 so that an experienced histologist could determine from a given 

 section the animal species from which the adrenal was ob- 

 tained. On the other hand, it is impossible to say from a study 

 of an adrenal from which order or genera it was derived. 

 Closely related species often have adrenals which differ widely 

 in their appearance. 



As we have already seen in the preceding chapter, the adre- 

 nals as compound organs are first encountered in the amphibia. 

 In the fishes the interrenal and chromaphil tissue are present 

 as separate organs. In the bird these two types of tissues are 

 intimately mixed. The interrenal tissue (corresponding to the 

 cortex of the mammal) is arranged in the bird in irregular 

 columns surrounding the blood vessels. The latter form a 

 network of irregularly arranged sinusoids throughout the 

 gland. The columns of interrenal tissue are called the " chief 

 strands" because they appear to form the foundation for the 

 other elements of the glands. The chromaphil cells have no 

 regular arrangement but occur in groups of 2 or 3, to 30 to 

 40 cells which, for the most part, lie in direct contact with the 

 venous sinusoids. The chromaphil elements are denoted as 

 the "intermediate strands." 



On cross section the adrenals of the mammal are seen to 

 consist of an external (or cortical) and an internal (or medul- 

 lary) portion. The former which constitutes the chief part of 

 the organ is usually of a deep yellow color, due to the presence 

 of lipids, while the latter is soft and pulpy and of a dark red- 

 dish or brownish color due to the presence of blood. In cattle, 

 the cortex when viewed soon after slaughter of the animal is 

 either ochre-yellow or brownish red, depending upon the age, 

 sex, and nutritive state of the animal, while the medulla pre- 



