NUTRITION AND GROWTH: I. 7 



The food was prepared fresh every day, or every second day. The foods used 

 were rice, canned condensed milk, sugar, and, later, commercial corn starch and 

 meat. The meat was obtained fresh from cold storage; the fat was cut away 

 and the rest passed through a grinder. Each food material was weighed and 

 boiled with water in a weighed pot after adding sodium chloride or other salt 

 mixtures.. After cooling, water was added to a certain weight, the mixture stirred 

 carefully, and the portion for each animal weighed. At the same time 50 or 100 

 grams of the mixture were placed in a large, well-closed jar with formalin until 

 food specimens for twenty-five or fifty consecutive days were collected. These 

 mixtures were used for analysis. Only meat and starch were fed to the animals 

 during the greater part of the experiments. 



The mixture at the beginning consisted of 1 part of starch and 10 parts of 

 meat; later of 1 part of starch and 2.5 parts of meat. One hundred grams of 

 food therefore consisted of 40 grams of meat; 16 grams of starch; and 44 grams 

 of water and salts. 



The animals were fed every forenoon between 9 and 10 o'clock. Each dog was 

 transferred to a small cage and kept there until it had finished eating. During 

 the first few weeks, it was necessary to give the food in two portions. After 

 that period every dog ate his entire amount in from five to ten minutes. 



The animals were weighed every one or two days before being fed, in order 

 to have an exact control of their body weights as an indication of growth or of 

 cessation of growth. The weights are recorded at intervals of five days so as not 

 to make the tables too cumbersome. I have also prepared charts showing the 

 weight of the animals and the amount of food administered at successive intervals. 



At the conclusion of an experiment the entire animal was analyzed. The 

 main object was to determine the weight and composition of the different parts 

 of the body; particularly the percentage of the important constituents such as 

 water, protein, and fat. 



Dissection had to be done very quickly in order to avoid the rapid decom- 

 position due to this climate. After the weight of the fresh material had been 

 determined formalin was added. Formalin, while rendering work with the mate- 

 rial rather disagreeable, nevertheless served admirably as a preservative and in no 

 way affected the accuracy of the results of the analyses. It is a safe disinfectant, 

 does not contain inorganic constituents, and can be removed readily by evapora- 

 tion. 



As a rule, it is very difficult to grind elastic or connective tissue in mills or 

 grinders, even if the tissue is well dried. After being in contact with formalin 

 it becomes hard and brittle. The formalin method effects the same result, there- 

 fore, as the more complicated one of freezing the tissues and passing them through 

 a special grinder. By using formalin it is easy in a few hours to grind thoroughly 

 in a small meat grinder the entire body of a dog weighing 5,000 grams. 



In the first experiment the animals were killed with ether, but in the later ones 

 by cutting the large blood vessels of the neck, the blood being collected in a 

 weighed porcelain dish; then the body was placed in a large tared dish and the 

 weight noted. The abdomen was opened and the gastro-intestinal tract ligated 

 at the cardia and the rectimi, and removed; the weight of the whole tract with 

 the contents intact was taken. Following this the stomach and intestines were 

 opened, the contents removed, and the gastro-intestinal tract cleaned and weighed 

 again. Now organ after organ was separated, weighed {the necessary cross- 

 sections being made to exclude gross pathologic changes ) , and placed with the 

 others in a weighed, salt-mouthed bottle which was closed air-tight by means of 

 a sheet of rubber and a wire fastener. Then from 40 to 50 cubic centimeters of 



