290 Biology in America 



by a like period of comparative freedom, thus insuring oppor- 

 tunities for an abundance of fresh air and exercise." 



In order to test the effects of a proteid-poor diet on dogs 

 living under conditions as nearly ideal as possible a series of 

 experiments were carried out on some twenty animals, 

 some of these lasting an entire year, ''AH of the . . . dogs 

 . . . were fed on a mixed diet, with some fresh meat each day ; 

 bread, cracker dust, milk, lard, and rice being the other foods 

 drawn upon to complete the dietary. The animals were fed 

 twice a day, each meal being accurately weighed and of defi- 

 'nite chemical composition. A large, light, and airj^ room, kept 

 scrupulously clean, and in the winter time properly heated 

 by steam, served as their main abiding place. In this room 

 were a suitable number of smaller compartments, the walls 

 of which were composed of open lattice work (of iron), so 

 as not to interfere with light or air, and yet adequate to keep 

 the dogs apart. These compartments were not cages in the or- 

 dinary sense, but were truly large and roomy. ... In pleas- 

 ant weather, immediately after their first meal, the dogs were 

 taken out of doors to a large enclosure near by, where they 

 were allowed perfect freedom until about four o'clock, when 

 they were taken in for their second meal (between four and 

 five o'clock in the afternoon). The outdoor enclosure was 

 inaccessible to every one except the holder of the key, and 

 the dogs while there were wholly free from annoyance. Once 

 every month, during a period of ten consecutive days, each 

 dog was confined in the metabolism cage so as to admit of 

 the collection of all excreta, in order to make a determination 

 of the nitrogen balance. Practically, therefore, each dog 

 was in close confinement only one-third of the month, the 

 remaining two-thirds being spent in much more congenial 

 surroundings." 



While details regarding all of these experiments cannot be 

 given here one case may be selected as an example. "The 

 animal employed in this experiment . . . was apparently full 

 grown, but was thin and had the appearance of being under- 

 fed. At first, it was given daily 172 grams of meat, 124 grams 

 of cracker dust, and 72 grams of lard. . . . (Later) a radical 

 change was made in the diet, by reducing the amount of meat 

 to 70 gi-ams daily ; . . . the cracker dust and lard being kept 

 at essentially the same levels as before . . . the dog in the 

 meantime gaining in body-weight. ... In this manner, the 

 experiment was continued with frequent changes in the char- 

 acter of the diet, but always maintaining essentially the same 

 (food) values . . . (for) just eleven months, with the ani- 

 mal at the close of the experiment still gaining in body- 

 weight, . . . and with every indication of good health and 



