820 



SCIENCE. 



[N.S. Vol. XXV. No. 647 



cent, in February, 1906, and at no time 

 since has it fallen below 22.2 per cent. 



The percentage of samples containing 

 fewer than 50,000 has never fallen below 

 50 since September, 1905, three months 

 after inspection work began. 



Experiments on the Germicidal Action of 



Fresh Cow's Milk: P. G. Heinemann. 



The question whether fresh cow's milk 

 contains bactericidal substances or not has 

 been answered in the affirmative by Fokker, 

 Ehrlich and Brieger, Park, KoUe and his 

 coworkers, Hunziker, Hippius, Koning, 

 and others. In opposition to this, Moro, 

 Honigmann, Basenau, Stocking and others 

 have denied ,the existence of such sub- 

 stances. 



Experiments by the writer carried on 

 by inoculating raw milk and milk heated 

 to 56° C. and to the boiling point indicate 

 that fresh cow's milk contains germicidal 

 substances, although to a smaller degree 

 than blood serum. Milk was obtained di- 

 rectly after milking and divided into three 

 portions, one of which was heated either to 

 boiling or kept at 56° C. for 30 minutes. 

 The second part was left without further 

 treatment, and then both heated and raw 

 milk were inoculated with suspensions of 

 bacterial cultures. The third part was 

 kept as control. Plates were prepared 

 from suitable dilutions and the colonies 

 counted after two days incubation at 37° C. 

 The three lots of milk were kept at room 

 temperature and plating repeated at regu- 

 lar intervals. The results lead to the fol- 

 lowing conclusions: 



Conclusions. — 1. Raw milk contains sub- 

 stances which are germicidal to a pro- 

 nounced degree for some species of bac- 

 teria. (B. coli, B. dysenteriw (Flexner), 

 B. fluorescens, non-liquefaciens.) 



2. Raw milk contains substances which 

 have slight germicidal action on some 

 species of bacteria. {B. violaceus, B. 



cholercB suis, B. prodigiosus (laboratory 

 culture), and some saprophytes isolated 

 from milk.) 



3. The germicidal substances in milk do 

 not act strongly on B. fluorescens lique- 

 faciens, B. typhosus, some varieties of B. 

 prodigiosus and B. proteus, but the multi- 

 plication of these organisms is restrained 

 for a limited period. 



4. The germicidal action of cow's milk 

 persists for more than 5 hours and less than 

 7 hours at room temperature. 



5. The germicidal action of cow's milk 

 is destroyed by keeping milk at 56° C. for 

 30 minutes or by heating to the boiling 

 point. 



6. The germicidal substances in cow's 

 milk are less powerful than those of blood 

 serum, but are inactivated under similar 

 conditions. The relative concentration of 

 these substances varies in milk from differ- 

 ent animals. S. C. Prescott, 



Secretary 



SCIENTIFIC BOOKS 

 Experimentelle Beitrage zur Morphologic. 

 Hefte I. and II. Herausgegeben von. Her- 

 man Braus (Heidelberg). Leipzig, W. 

 Engelmann. 1906. 



The study of experimental morphology, 

 which in recent years has attracted so large a 

 body of enthusiastic students, has been taken 

 up very largely from the dynamic or physi- 

 ological point of view. This is indicated by 

 the title of the journal most specifically de- 

 voted to this line of work — W. Eoux's ' Ent- 

 wieklungsmechanik der Organismen.' Tet, 

 although some physiologists, like Pfliiger and 

 Loeb, have done much to stimulate interest 

 in this direction, it is chiefly to professional 

 zoologists and anatomists that the subject has 

 appealed, while the immediate predecessors and 

 many of the contemporaries of these same 

 zoologists and anatomists have been interested 

 rather in phylogenetic and historical than in 

 dynamic biological questions. 



The purpose of these Beitrage is to empha- 

 size the value of experimental and accidental 



