140 THE VITAMINES 



typical rosary. The animals were very little resistant to infections, 

 were apathetic, lethargic and extremely unwilling to exert them- 

 selves, at a time when the existing bone changes could not yet have 

 been responsible. This was undoubtedly due to the impairment of 

 the muscular tonus. 



After death, the bones were found to be very poor in calcium and 

 showed,, in the X-ray, an appearance characteristic of rickets, as 

 may be seen in the illustration. Of two dogs of the same litter, 

 one animal received only the "rachitic" diet, the other, vitamine A 

 in addition. The malformation of the cartilage epiphyses and the 

 more frequently occurring osteoid tissue are the two chief symptoms. 

 According to Henderson (408c) the muscle of the rachitic dog con- 

 tains less creatine than the normal. Findlay, Paton and Sharpe 

 (408b) conducted metabolism experiments on rachitic dogs. A cal- 

 cium-poor diet caused osteoporosis, but not rickets, while in rachitic 

 dogs the blood and the tissues showed the normal calcium content. 



The significance of Mellanby's experiments for the study of rickets 

 will be discussed further in the description of this disease. 



In conclusion, we shall mention an investigation of Chittenden and 

 Underhill (I.e. 28). They fed dogs on cooked peas, zwieback and 

 cottonseed oil, and noted a disease which they believed to be anal- 

 ogous to pellagra in man. The disease developed after 2 to 8 months, 

 showing that a larger amount of peas was less harmful. The dis- 

 ease, which could be cured by adding meat to the diet, produced 

 ulcerations of the mouth; in particular, the entire enteron was 

 hemorrhagic. Besides, there was observed a great loss of weight, 

 peculiar gait and diarrhoea. If a part of the peas was substituted 

 by casein, the symptoms appeared sooner. This shows, perhaps, 

 that the condition is associated with a lack of vitamines, since peas 

 contain some vitamine but not enough. To our knowledge, this work 

 has not yet been repeated by any other investigator. 



Domestic animals 



We come now to the consideration of domestic animals, among 

 which we shall discuss goats, sheep, horses and pigs. In this field, 

 there are questions which are not yet quite clear, but which possess a 

 definite significance in their social and economic aspect. We have 

 very little accurate knowledge of the vitamine requirements of these 

 animals. In various parts of the world, we encounter diseases, 



