THE PITUITARY BODY 



by Nelson and Nelson (193 1), and Nelson and Woods (1934). 

 One of the most convenient methods appears to be that of 

 Burn (1931) who used rats to which he administered by 

 stomach-tube 5 cc. of water per 100 grams body-weight as 

 well as a posterior-lobe extract subcutaneously (dosage range: 

 ca. 0.002-0.012 unit per 100 grams body-weight). The assay 

 is based upon the time elapsing between the administration 

 of water and the maximum secretion of urine during periods 

 of 15 minutes. The elapsed time is naturally greater, the 

 larger the dose of extract. By using at least sixteen rats and 

 by referring to a previously constructed curve in which was 

 shown the relationship between dose and time elapsing until 

 maximum urinary secretion occurred, Burn could estimate 

 the potency of an extract with a maximum error of less than 

 + 20 per cent. Marx (1933) also has used the rat in assaying 

 the diuresis-inhibiting hormone. 



In the urine secreted during the inhibition of water 

 diuresis by posterior-lobe extracts or the vasopressor fraction 

 the concentration of chloride is increased — sometimes mark- 

 edly (see Fig. 55). This "chloride-concentrating" effect of an 

 extract may be investigated to strengthen the belief that the 

 effect of an extract is similar to the effect of the vasopressor 

 hormone. However, the phenomenon appears to be of little 

 value for purposes of quantitative assay. 



The toxicity of the active principles. — The toxicity of the 

 active principles of the pars neuralis has been approximately 

 determined in only a few animals. In mice it is said that the 

 "lethal dose" is 1,700 pressor units per kilogram body-weight 

 (total dose divided over 12 hours; Hill, Long, and Bischoff, 

 1932) or 6,000-8,000 units per kilogram body-weight intra- 

 peritoneally (Haferkorn and Lendle, 1933). According to 

 Voegtlin and Dyer (1924), the subcutaneous lethal dose in 

 the rat is about 2,200 units (1,080 mg.) per kilogram body- 

 weight; they considered the intravenous lethal dose to be 

 about 160 units per kilogram body-weight. Bischoff and 



[3^6] 



