.")()() 1>R()CESSE8 INFERRED FROM INDIRECT OBSERVATION 



emulsified and administered by hypodermic injection, brings about an 

 acceleration of the growth of inoculated carcinoma in rats which is 

 just as marked as that which is caused by cholesterol. By extraction 

 with alcohol and subsequent precipitation with ether a substance is 

 obtained from the dried tissue of the anterior lobe of the pituitary 

 body which has been designated Tethelin. This substance is evidently 

 a lipoid, for it yields fatty acids on hydrolysis, but it is a lipoid of very 

 exceptional physical and chemical characteristics. It is soluble in water, 

 alcohol or ether, but insoluble in a mixture of certain definite pro- 

 portions of alcohol and ether. It is present in ox-glands to the extent 

 of about 0.7 per cent, of the fresh anterior-lobe tissue. The adminis- 

 tration of four milligrams of this substance per day to mice from five 

 weeks of age onward produces a most decisive change in the velocity 

 and time-relations of growth. The effect is similar in kind to that of 



d 



70 80 



WEEKS 



FIG. 41. Influence of tethelin upon the growth of male white mice. The vertical 

 cross-mark indicates average duration of life. 



the administration of pituitary tissue itself, that is, initial retardation 

 followed by acceleration, but both effects are exaggerated so greatly as 

 to involve total distortion of the curve of growth, the second growth- 

 cycle appearing to be prolonged while the third or adolescent cycle is 

 abbreviated and accelerated* (Fig. 41). The quantitative difference 

 between the growth-effects obtained with tethelin and observed in 

 anterior-lobe tissue administration are attributable to the difference 

 m the dosage of tethelin which is received in the two cases. It is not 

 practicable, for example, to administer much more than a twelfth of 

 a fresh ox-gland per day to mice, because the quantity of meat consumed 

 would otherwise constitute an important abnormality in the diet. 

 Phis amount of pituitary tissue, however, contains only between eight 

 and nine-tenths of a milligram of tethelin, or one-fifth the amount 

 administered in the experiments cited above. 



