546 U. ff. BUREAU OF FISHEEIES 



impulse, regulation of heart beat, coagulation of the blood, reproduc- 

 tion, gland secretion, cell permeability, and other vital processes 

 depend on proper amounts of these elements that remain in the ash 

 on ignition. The important question concerning them for the general 

 reader is. Do they occur in sufficient quantities and proper proportions 

 in our daily diet? 



There is believed to be a danger of deficiency and disproportion 

 in some of them. We demand our food highly cleaned and selected, 

 and parts containing valuable mineral substances such as husks, 

 peelings, bones, and skins are frequently discarded. If, for example, 

 in our meat foods we should grind up the entire animal and eat 

 equal proportions of it all we would get about the proper amounts 

 of mineral ; but we discard bones and often glands, and prefer muscle 

 tissue, which contains more potassium than do the other tissues and 

 is deficient in calcium. Deficiency of iodine is at the danger point 

 in many localities. 



Table 22 shows that that part of fish which we usually eat con- 

 tains relatively raore calcium than other meat foods do. This ap- 

 plies particularly to such canned fish as salmon and sardines, where 

 the bones are softened and edible. It applies also to shellfish, such 

 as oysters and clams, where the shell-secreting mantle contains a 

 high percentage of calcium. The livers of shellfish also contain 

 much iron. Fish, especially salt-water fish and shellfish, generally 

 contain much iodine and are particularly valuable in this respect. 

 Concerning the possible value of the heavy metals in fish we have no 

 exact data at present. 



It seems permissible to conclude that fish as a class are a safeguard 

 against mineral deficiencies in the diet, and that they deserve more 

 attention than they have had from chemists and dieticians from this 

 point of view. 



V.-VITAMINS IN FISH AND SHELLFISH 



By E. v. McCoLLUM, Professor of Chemical Hygiene, School of Hygiene and 

 Public Health, Johns Hopkins University 



On the evidence brought to light by the extensive researches in 

 the field of foods and nutrition during the last 20 years, it is now 

 universally believed that there exist a number of chemical sub- 

 stances that are indispensable for normal nutrition in man and 

 animals. When one or another of these is left out of an otherwise 

 complete diet, certain pathological symptoms appear, which can be 

 produced in no way other than hj vitamin deficiency. The diseases 

 characteristic of vitamin deficiency can be prevented or cured only 

 by the inclusion in the diet of the vitamin with which each is asso- 

 ciated. No one or more of the vitamins can be omitted from the 

 diet without profound disturbance to health. Fortunately, most 

 of our ordinary foods contain at least small amounts of one or more 

 of them, so that when we eat a fairly wide variety of natural foods 

 the danger of vitamin deficiency is small, except in the case of a 

 single one, viz, vitamin D. 



The vitamins arc of unknown chemical nature and are known by 

 the names vitamin A, vitamin B, vitamin C, vitamin D, and vitamin 

 E. A lack of vitamin A in experimental animals caused the appear- 

 ance of an eye disease, which results from a loss of power of the tear 



i 



