Quotes Leslie J. Harris, Vitamins in Theory and Practice (Cambridge: University Press, 1935).
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'Dr. Leslie Harris, in his book "Vitamins in Theory and Practice," says: "Dogs do not need any vitamin C in their diet, because they are able to manufacture it in their own bodies. In fact, the only species which cannot make their own vitamin C, and must therefore be given it in their diet, are, so far as out present knowledge goes, man, monkeys and guinea-pigs." This being so, and it has been amply established by several investigators, the argument that vegetables should be given [to dogs] raw collapses, for while vitamin C might be affected by cooking, vitamin A, which is the only other vitamin which they supply in significant degree, would not.'

Quotes Medicus, 'Notes for Novices: Vitamins', Our Dogs 116 (21st July 1939), p. 179.
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Sir,- In his "Notes for Novices" which appeared in your issue of July 21, "Medicus" commits himself to certain statements which are somewhat at variance with scientific belief. Perhaps you will allow me to offer a few comments. The sentences in inverted commas are quotations from his article.

"The two vitamins of greatest importance to dog owners are A and D." Vitamin B, however, is equally vital. Actual experiments on dogs have shown that an insufficiency will result in loss of appetite, and in extreme cases in paralysis and death, and its presence is necessary to successful reproduction. Generally speaking, the supply of this vitamin will be adequately met if wholemeal biscuit forms the basis of one or two daily feeds. In the case of puppies under three months, where I do not favour wholemeal biscuit, or during the reproductive period, it seems advisable to supplement the vitamin B content of the diet, and I have found Marmite excellent for this. It appears to be extremely palatable to puppies, and has a potency comparable to that of yeast - of which it is in fact a preparation.

"Puppies can be cured of rickets... by the use of yeast, which is rich in vitamin D." Yeast is not rich in vitamin D unless it has first been irradiated by ultra-violet rays. It contains a substance called ergosterol, which when activated by these rays produces vitamin D, so that unless the yeast has been subjected to this irradiation it will have little effect on rickets. Yeast is pre-eminently a source of vitamin B, and must be in specially prepared form if it is to be regarded also as a source of vitamin D.

Later he goes on to stress the importance of raw vegetables as a medium for vitamin C. Dr. Leslie Harris, in his book "Vitamins in Theory and Practice," says: "Dogs do not need any vitamin C in their diet, because they are able to manufacture it in their own bodies. In fact, the only species which cannot make their own vitamin C, and must therefore be given it in their diet, are, so far as out present knowledge goes, man, monkeys and guinea-pigs." This being so, and it has been amply established by several investigators, the argument that vegetables should be given raw collapses, for while vitamin C might be affected by cooking, vitamin A, which is the only other vitamin which they supply in significant degree, would not. Furthermore, it should be remembered that the nutrients in vegetables are enclosed in envelopes of cellulose, which is difficult of digestion of by the dog. Boiling, however, splits the cellulose and renders the contents vulnerable to the action of the digestive juice. Quantatively, carrots are not a good source of vitamin A when one considers the available alternatives. Even if the content of that vitamin were in assimilable form - which it certainly is not - it would take about three and a half ounces of them to give an equivalent amount of vitamin A to that of one ounce of cow's liver or one tablespoon of cod-liver oil.

Most of these points were dealt with in my articles on "The Dog and His Diet," which appeared in Our Dogs of August 12, 19 and 26, 1938.' (336)

 

Relevant passages from article by 'Medicus':

'The two vitamins of greatest importance ot dog oweners are A and D...

Vitamin D is the preventative of rickets, and its discovery and the developments followng its discovery have revolutionised medical and veterinary science where rickets are concerned.'

'Rickets in children is cured nowadays by the administration of cod-liver oil and halibut oil (the latter is stronger in vitamin D), and at the same time by sunlight and ultra-violet ray treatment. Puppies can be prevented from having rickets by administering these oils from fish-livers, and also by the use of yeast, which is rich in vitamin D. Yeast in various qualities is now advertised in specially prepared form for dogs, and it is always a wise precaution to let growing puppies have a proportion of it - especially those of the long-legged, heavy-bodied varieties. Special preparations of yeast are, I notice, regularly advertised in Our Dogs.

...

I must not omit to mention vitamin C... It occus in fruits and green vegetables, and that is why it is always advantageous to give dogs - especially puppies - some form of green vegetable food mixed in with their ordinary feeds. It is a mistake, however, to give cooked vegetables. I find so many people make this error. Cooking, especially with salt and soda (often used by the poorer classes) will destroy the vitamins, and the dog would be better without any such addition to his food. The way to give scraped carrot or finely dessicated cabbage is by mixing with wholemeal biscuit and pouring meat gravy over the whole. As a matter of fact, where speedy addition of vitamin C is required, the best way to give it is in the form of orange-juice or tomato-juice. That is what happens in human practice.' (179)