Experimental Rickets. 



61 



phosphate. In case of adding too much alkali it is best to use 

 acetic acid to bring the solution back to Ph = 4, because the 

 danger of overstepping the end point is very small, since the 

 mixture of sodium acetate and acetic acid can vary considerably 

 in composition with little change in the hydrogen ion concentra- 

 tion. This is McCrudden's method in principle, but the indicator 

 makes us more certain of the P H . The calcium oxalate was 

 titrated with potassium permanganate. 



We do not wish to discuss the diagnosis of rickets, although 

 our animals showed the same appearances as those described in the 

 papers of Sherman, McCollum and Hess. Dr. C. M. Jackson has 

 very kindly offered to work out the morphological changes in great 

 detail and publish them so that they will be available. From a 

 practical standpoint, however, types of non-rachitic osteoporosis 

 caused by calcium deficiency do not seem to be very common 

 among human beings. Bone abnormalities which are possible 

 on human diets at present in use deserve considerable study 

 whether they are called rickets or not and we use the word rickets 

 merely for convenience. Some of our rats getting more phosphoric 

 acid than that contained in the wheat flour seemed to recover 

 from the disturbance of metabolism just as infants may recover 

 from rickets, with the reservation that the diets of our rats were 

 unchanged in percentage-composition and only changed in the 

 quantity eaten per day, whereas very little exact data is to be 

 had on the diets of human beings. In case the abnormalities 

 are not great enough to cause permanent deformities we do not 

 know of any means of detecting the previous history of rickets 

 without diagnosing it at the time of its occurrence. The x-rays 

 and calcium balances, however, may be used for diagnostic 

 purposes on rats without killing the animals. Rats die easily 

 under ether and it is difficult to get them absolutely quiet without 

 danger of killing them unless they are held mechanically. They 

 may be stretched out by tying their feet to a stiff ring of suitable 

 size after slightly etherizing them. 



