THE SUMMER DIARRHCEAS OF INFANCT. 91 



rhcea of infancy, are probably only putrefactive or saprophytic in 

 character, and that they prove harmful by producing toxins ; while 

 those that cause the choleraic form or serous diarrhoeas, are more 

 than putrefactive, they are pathogenic. At that time it was gener- 

 ally believed that a specific germ would be found ; but the truth of 

 the above statement has been made more manifest with every ex- 

 perimental study of the subject. More recently, Booker ' makes the 

 following statement : " No single microorganism is found to be the 

 specific exciter of the summer diarrhoeas of infancy, but the affection 

 is generally to be attributed to the result of the activity of a 

 number of varieties of bacteria, some of which belong to the well- 

 known species and are of ordinary occurrence and wide distribution, 

 the most important being the streptococcus and proteus vulgaris." 



Vaughan has studied the chemical properties of the germs x, a 

 and A of Booker's list in the following manner and with the result 

 as stated below : Beef broth cultures were kept in the incubator at 

 37° for ten days. They were then twice filtered through heavy 

 Swedish filters, and the second filtrate was allowed to fall into a 

 large volume of absolute alcohol, feebly acidified with acetic acid. 

 A voluminous, flocculent precipitate resulted in each case, and after 

 subsidence the supernatant fluid was decanted. The precipitates 

 were then treated with distilled water, in which those from x and a 

 were soluble, while that from A proved insoluble. A large volume 

 of absolute alcohol was again added, and the mixture allowed to 

 stand for four days. The precipitates from x and a completely 

 subsided, leaving the supernatant fluids perfectly clear ; but in the 

 case of A the subsidence was not complete. The precipitates were 

 <3ollected, by decantation and filtration, on porous plates, and dried 

 over sulphuric acid. These substances are proteid in composition 

 but differ from known proteids and from one another. That from x 

 is slightly yellow, as seen deposited in the alcohol, but becomes 

 grayish on exposure to the air. It is readily soluble in water from 

 which it is precipitated by either heat or nitric acid, singly or combined. 

 It gives the biuret and xanthoproteic reactions and is precipitated 

 by saturating its aqueous solution with ammonium sulphate, and 

 therefore cannot be classed with the peptons. Sodium sulphate and 

 carbonic acid fail to throw it down from its aqueous solution ; conse- 

 quently it is not a globulin, and for the present at least it must be 

 classified among the albumins ; however, it possesses properties which 

 do not belong to the known albumins. 



The proteid prepared from cultures of the germ a is, as seen under 

 the alcohol, very Ught, flocculent, and perfectly white ; but so soon 

 as it is brought in contact with the air it begins to blacken, and 

 finally dries down on the porous plate in black scales. It possesses 

 the same general properties in regard to the action of solvents and 

 ^ Johns Hopkins Hospital ReporU, 6, 1897. 



