106 Microscopic Histochemistry 



a high degree of unsaturation. On prolonged storage, even 

 depot fat will develop more or less intense aldehyde reac- 

 tions. HgCL has httle effect on the formation of aldehyde 

 from unsaturated fatty acids. Periodic acid, on the other 

 hand, produces large amounts of aldehyde.^^ Plasmalogen as 

 a source of aldehydes is probably much less important quan- 

 titatively than unsaturated fatty acids. 



The question is vv^hether there may be any nonaldehydic 

 substances in the tissues which could give positive reactions 

 with the reagents mentioned. 



The first group of compounds to be considered are the ke- 

 tones. Some of them may result form the oxidation of un- 

 saturated fatty acids (especially by the rearrangement of 

 epoxides^^), but there is no positive proof for their existence 

 in animal tissues. On the other hand, ketosteroids are known 

 to be present in a number of tissues. They give no color with 

 Schiff's reagent,^^' ^^ which is fairly specific for aldehydes; but 

 there can be no doubt that they would give good positive 

 reactions with most other carbonyl reagents. Actually, the 

 reaction obtained with phenylhydrazine^* or with 2-hydroxy- 

 3-naphthoic hydrazide^^ has been assumed to be indicative of 

 the presence of ketosteroids. However, the evidence adduced 

 is of only a circumstantial nature. Dempsey^^ says that, while 

 not one of the physical and chemical features (carbonyl reac- 

 tions, Schultz test, birefringence, fluorescence, solubility in 



60. Wolman, H.: Proc. Soc. Exper. Biol. & Med., 75:583, 1950. 



61. Foumeau, E., and Tiffeneau, M.: Compt. rend. Acad, sc, 144:662, 



1905. 



62. Albert, S., and Leblond, C. P.: Endocrinology, 39:386, 1946. 



63. Oster, K. A., and Oster, J. G.: J. Pharmacol. & Exper. Therap., 

 87:306, 1946. 



64. Bennett, H. S.: Proc. Soc. Exper. Biol. & Med., 42:786, 1939; Ben- 

 nett, H. S.: Am. J. Anat., 67:151, 1940; Dempsey, E. W., and Bassett, 

 D. L.: Endocrinology, 33:384, 1943; Deane, H. W., and McKibbin, J. M.: 

 Endocrinology, 38:385, 1946; Deane, H. W., and Creep, R. O.: Am. J. 

 Anat., 79:117, 1946; Creep, R. O., and Deane, H. W.: Anat. Rec, 97:416, 

 1947; Creep, R. O., and Deane, H. W.: Ann. New York Acad. Sc, 50:596, 

 1949; Applegarth, A.: Endocrinology, 44:197, 1949. 



65. Dempsey, E. W.: Recent Prog. Hormone Research, 3:127, 1948. 



