I. THE ORIGIN OF VIRUSES 131 



patient feces (5). 



The existence of an intimate relation between the kind of diet 

 and the phage excretion into the chicken feces is apparently brought 

 about by the difference in the digestibility or coarseness of the diet. 

 Thus, if a diet consists of coarse, indigestible materials, the defecation 

 will readily occur in favour of the phage preservation which will further 

 be effected by the envelopment of the phage by these coarse, indigesti- 

 ble materials so as to be protected from the action of destructive agents 

 which may be present in the alimentary tract. 



Wheat bran, as mentioned above, v/as highly effective in the phage 

 excretion but its water or alcohol-ether extract had no action, though 

 the residue was somewhat effective. Moreover it was confirmed that a 

 coarser bran could excrete phage more readily than finely smashed one. 

 Further, wheat bran is the crust of wheat grains, but wheat grains 

 themselves proved to be inactive. There seems no doubt, therefore, 

 that the effectiveness of some diet in phage excretion was chiefly go- 

 verned by its physical rather than its chemical properties. 



In the feces of animals such as mice, rats, guinea-pigs, and rabbits, 

 the phage detection was generally difficult, whereas in those of dogs 

 or donkeys it was usually easy, a fact possibly dependent upon the 

 property of feces which varies with the species of animals, the coar- 

 seness of the ingredient or the speed with which the food residues pass 

 the digestive tract may play an important role. The digestive fluids 

 likewise may vary with animals and may have some connection with it. 



Phage seems, however, not always produced by animal organs, 

 since the phage detection in chicken feces is only possible in summer 

 or at least in warm seasons ; in winter no phage is found even when 

 the chickens are fed wheat bran or led to diarrhoea by the administra- 

 tion of castor oil. The cells of organs, therefore, seem to alter with 

 the change of seasons in their character of producing phage; in winter 

 may fall into a state unable to produce the phage. Thus the property 

 of the cells of producing phage may not be constant, and may possibly 

 be altered by proper agents other than the seasonal effect. The above 

 mentioned action of castor oil or some diets such as wheat bran might 

 be accordingly not only dependent upon their properties to hinder 

 phage inactivation but also upon some other properties which may 

 cause the cells to produce phage. 



In addition to the phage having thus its origin in animal organs, 

 there appears to be another group of phage. It is generally known 

 that certain bacteria produce an agent capable of acting as a phage 

 upon certain other bacteria. Such bacteria are termed lysogenic. There 

 seems therefore two groups of phage, one of which is produced by 

 lysogenic bacteria and the other by certain animal cells. 



