252 CORTEX 



as the presence of excess salt in the diet. It is only necessary 

 to determine the amount of a given extract necessary for 

 maintaining normal growth during the week following adrenal- 

 ectomy, to obtain an accurate estimate of the potency of the 

 extract. 



The operative technique. Complete adrenalectomy is much 

 more easily performed in the month-old rat than it is in adult 

 animals. The muscles and connective tissue are so delicate 

 and thin that they are practically transparent. The blood 

 vessels are so small that ligatures or other forms of hemostasis 

 are unnecessary. The rat is not prone to pyogenic infections 

 and hence an aseptic technique is also unnecessary. 



The animal is anesthetized by an intraperitoneal injection 

 of a solution of one of the barbiturates. Nembutal has been 

 found satisfactory for this purpose. About 0.8 mgm. of this 

 drug is required for a month old rat. There is a considerable 

 individual variation in the amount of anesthetic necessary and 

 hence it is desirable to inject first the minimal dose producing 

 anesthesia and then repeat with a second small dose when 

 necessary. 



When the animal is deeply anesthetized it is placed on a 

 small block and the hair over the lumbar region is moistened 

 with water. Shaving the operative site is not necessary. 

 The skin over the spine is now lifted with a forceps and a single 

 transverse incision is made through the skin, at the level of the 

 costal margin and extending for about 2 centimeters across the 

 back (Figure 14). 



To facilitate the removal of the adrenals, it is desirable that 

 the incision through the lumbar muscles be made as nearly as 

 possible over the site of these glands. On the left side, the 

 spleen is used as a convenient landmark. This organ appears 

 as a black shadow through the thin lumbar muscles. A tiny 

 incision|is made into these muscles at the posterior border and 

 about 5 mms. below the upper margin of the splenic shadow. 

 The incision is widened by inserting and spreading the scissors. 



