82 SUMMARY OF CURRENT RESEARCHES RELATING TO 
pigment, so the bacillus of blue milk is found to become in similar 
circumstances incapable of developing its characteristic pigment. Of 
this defect Dr. P. Behr narrates four examples. The specimens were 
obtained from cultivations made by competent observers. These four 
achromatic species were cultivated by the author on various media, such 
as gelatin, agar, potato, milk, and the results are compared in a series of 
four tables. This loss of the chromogenic function is possibly only a 
temporary aberration. 
Colour and Pathogenic Differences of Staphylococcus pyogenes 
aureus and S. albus.* — MM. Lannelongue and Achard attack the view 
expressed bvRodet and Courmont, that Staphylococcus pyogenes aureus is 
identical with S albus, and that the one easily passes into the other. 
Although S. aureus , even in fresh cultivations and in oklones, frequently 
loses its colour, yet this colour can always be obtained again by breeding 
from a fresh cultivation, while the white can never be thus changed into 
orange. 
The pathogenic properties of the two micro-organisms are of different 
intensity, those of S. aureus being much stronger than those of S. albus. 
Acid- and Alkali-formation by Bacteria.t — Dr. T. Smith gives 
details of some interesting experiments corroborative of the influence of 
sugar in causing the formation of acid in certain bacterial cultiva- 
tions. Hog cholera bacillus /3 was inoculated on four media: — 
(1) Pepton bouillon ; (2) pepton bouillon with one drop of 10 per 
cent, glucose solution ; (3) pepton bouillon with two drops sugar 
solution ; (4) pepton bouillon with four drops sugar solution. In 
twenty-four hours (1) was slightly alkaline, (2) and (3) were slightly 
acid, and (4) strongly acid. After seven days (1), (2), and (3) were 
alkaline, but (4) remained acid. 
A similar set of experiments was made with typhoid bacillus. Iu 
24 hours all were distinctly acid. After 10 days the sugarless solution 
had become alkaline, the other three remaining acid. 
The inference from these observations seems to be that by the 
judicious addition of small quantities of sugar an increased growth of 
many alkali-forming bacteria may be induced, the acid derived from the 
sugar diminishing the alkalinity of the cultivation. 
Germicidal Action of the Blood in different conditions of the 
organism.^ — The experiments of A. Rovighi embraced the germicidal 
property of normal blood, that of definite disease, and that where the 
condition was merely febrile. Experiments were also made to determine 
the optimum temperature of germicidal action. By employing Buchner’s 
method, the following results were obtained. The blood of healthy men 
possesses the property of completely destroying the typhoid bacillus, 
while on Staphylococcus pyogenes aureus and Friedlander’s pneumo- 
bacillus it exerts a transient and less energetic action. 
In blood taken from pneumonia patients, the germicidal influence 
* La Semaine Med., 1890, No. 25. See Centralbl. f. Bakteriol. u. Parasitenk., viii. 
(1890) p. 429. 
t Centralbl. f. Bakteriol. u. Parasitenk., viii. (1890) pp. 389-91. 
* Riforma Med., vi. (1890) p. 656. See Centralbl. f. Bakteriol. u. Parasitenk., viii. 
(1890) p. 561. 
