II. CHEMISTRY 169 



times applied to all bluefins; this was later corrected^^" to T. saliens, the 

 California bluefin, m accordance with the Jordan classification. ^^^) 



Confirmation of this work appeared in the studies of Haman and Steen- 

 bock"- and Black and Sassaman.^^* It was shown^^^ that a commercial, 

 mixed-species tuna liver oil was "somewhat less effective" on chickens, 

 per rat unit, than other oils which were compared. Repeated trials"^ with 

 three Japanese species of tuna (bluefin, striped, and yellowfin) showed that 

 the liver oils were only from 40 % to 63 % as effective, rat unit for rat unit, 

 as cod liver oil on chickens. Bills et a/.^*° extended the work with the oils 

 of twenty-five species of fish. They found conspicuously low efficacy ratios 

 for albacore, striped tuna, totuava, and California bonito, as well as for 

 the original California bluefin tuna. Several other species, especially white 

 sea bass and Pacific dogfish, appeared to have efficacy ratios that were 

 distinctly above par. 



It is true, nevertheless, that most fish oils have an efficacy ratio of around 

 100, the value characteristic of cod liver oil and activated 7-dehydrocholes- 

 terol (vitamin D3). Thus sardine (pilchard) body oil, which Bills ^^"^ in 

 1927 found similar to cod liver oil in assays with rats, has for many years 

 been successfully used in poultry raising. Rygh^^^ could recognize no signifi- 

 cant differences in the efficacy ratios of the liver oils of seventeen species of 

 fish. Haman and Steenbock^^^ found that sardine body oil, halibut liver oil, 

 and burbot liver oil had about the same efficacy ratio as cod liver oil. Black 

 and Sassaman^^* found that the liver oils of cod, halibut, swordfish, and 

 Japanese mackerel were about the same in efficacy ratios. In the work of 

 Ryghisi and especially of Dols,^*^ the vitamin D of tuna liver oil was found to 

 have the same efficacy ratio as cod liver oil ; the tuna was the European blue- 

 fin, Thunnus thynnus, a species distinct from the California and Japanese 

 forms. 



The fact that cod liver oil and many other fish oils exhibit the efficacy 

 ratio of ^dtamin D3 is no proof that this is the one and only form of vitamin 

 D which these oils contain. It is possible that other forms are present which 

 are equally effective for rats and chicks, or that forms of higher and lower 

 efficacy ratio are present in admixture. Hickman and Gray^^^ utilized the 

 technique of molecular distillation in an investigation of the vitamin D of 

 several fish oils. They found at the outset that about 70 % of the vitamin 

 D of cod liver oil occurs as esters, and so it was necessary to conduct the 

 short path distillations with saponified material. Cod liver oil exhibited a 

 complex elimination curve indicative of two major, two minor, and two 



ISO C. E. Bills, O. N. Massengale, M. Imboden, and H. Hall, J. Nutrition 13, 435 (1937) . 



"««C. E. Bills, J. Biol. Chem. 72, 751 (1927). 



1" O. Rygh, Nature 136, 552 (1935). 



182 M. J. L. Dols, Z. Vitaminforsch. 5, 161 (1936). 



