CHOLESTEROL AND THE PHYTOSTEROLS 99 



(rats) inoculated with carcinomatous tissue, the cancer grows much 

 more rapidly than in normal animals and "metastases" or fresh growths 

 in localities distant from the site of the primary growth, are formed 

 much more numerously and in a much higher proportion of animals. 

 In this connection it is significant to observe that Carcinoma is primarily 

 a disease of old age so far as manifest growth or accretion of the parasitic 

 tissue is concerned. It very rarely manifests itself in man before thirty 

 and increases in frequency very decidedly with advancing age, the 

 incidence between the ages of sixty-five and seventy-five being no less 

 than ten times as great as between thirty-five and forty-five. It 

 is, however, impossible to initiate carcinomatous growths in animals 

 by administration of cholesterol, unless carcinoma-tissue is already 

 present as a result of inoculation or spontaneous development, so that 

 cholesterol cannot be looked upon as a cause, but rather as a favoring 

 condition of cancer-growth. It must be remembered that our estimate of 

 the age of incidence of carcinoma is founded upon the date at which the 

 growth obtrudes itself upon the attention of the patient or physician. 

 For how long prior to this its beginnings have been actually resident in 

 the body, we have no means of estimating, but judging by the analogy 

 afforded by other growth-phenomena (cf . Chapter XX) we may infer 

 that the date of origin of the growth probably precedes by a consider- 

 able interval the date of its obvious manifestation, so that despite the 

 fact that cholesterol cannot initiate cancer, the date of its diagnosis, 

 and therefore its "apparent" or "statistical" date of incidence may very 

 possibly be determined by the acceleration of its growth due to an 

 accumulation of cholesterol in the tissues. 



Cholesterol yields the following series of color reactions together 

 with others, for description of which the student is referred to special 

 monographs : 



Salkowski's Eeaction. Cholesterol is dissolved in chloroform and an 

 equal volume of concentrated sulphuric acid is added. The solution 

 is colored blood-red which changes gradually to purple. If the mixture 

 is poured out in a shallow layer and exposed to the air, the purple 

 changes to blue, then green and ultimately yellow. 



Liebermann-Burchard Reaction. Cholesterol is dissolved in a small 

 amount of chloroform in a dry test-tube, a few drops of acetic anhydride 

 are added and then concentrated sulphuric acid is added drop by drop. 

 The mixture becomes red, then blue and finally, if not too much 

 cholesterol and sulphuric acid have been added, a permanent green. 



Obermuller's Reaction. Dry cholesterol is heated in a glass tube with 

 two or three drops of propionic anhydride until it melts. On cooling 

 the mass turns first violet, then blue, green, orange, and finally red. 



Schiff' s Reaction. To dry cholesterol in an evaporating dish add a 

 trace of ferric chloride, strong hydrochloric acid and chloroform, and 

 evaporate the mixture nearly to dryness, when the edge of the residue 

 begins to turn violet. Then add more chloroform, evaporate to dry- 

 ness and heat. The whole mass turns violet first with a reddish and 

 later with a bluish nuance, and finally a dirty green. 



