METHODS OF REDUCING THE GERM CONTENT 541 



in raw milk and are rounded and shrunken. Nuclei are dis- 

 tinctly stained. The author of this method of staining claims 

 that with little practice the difference between heated and raw 

 milk becomes easily apparent. 



Attempts have been made to prolong the keeping quality of 

 milk and to render milk safe by means other than heat. Budde 

 in 1903 introduced a process known as "buddeizing." This 

 consists in adding 12 c.c. of hydrogen peroxid to 1 quart of 

 milk and keeping the mixture at 52 C. for several hours. The 

 majority of bacteria are destroyed, but a small excess of hydro- 

 gen peroxid imparts a disagreeable bitter taste to the milk. This 

 can be overcome by adding a catalase. "Hepin" is a catalase pre- 

 pared from the liver of a rabbit and has been used for this pur- 

 pose. However, the method is too complicated to be of practical 

 value and the rapid separation of cream after buddeizing is a de- 

 cided disadvantage. The process has never been popular and is 

 uncertain in results because of the variable potency of commercial 

 preparations of hydrogen peroxid. Some of these contain poison- 

 ous substances, such as mineral acids, acetanilid, arsenic or barium 

 salts, and at best are unstable products. 



Von Behring's recommendation to add formaldehyd to milk 

 has been given some attention. No detrimental results could be 

 observed when animals were fed with milk containing formaldehyd 

 in the proportion of 1 : 1250 parts of milk. Formaldehyd in 

 the proportion of 1 : 10,000 cannot be detected by means of the 

 senses and bacterial growth is inhibited for a number of days. The 

 amount recommended by v. Behring is 1 : 40,000. This amount 

 is not germicidal, but has a restraining effect on bacterial growth. 

 The benefit derived from its use is therefore doubtful, and con- 

 stant ingestion of even small quantities of formaldehyd is probably 

 harmful to infants. 



Destruction of bacteria by ultraviolet rays has been pro- 

 posed as a means of reducing the bacterial content of milk. Ayers 

 and Johnson have made a comprehensive investigation of the 

 value of this method. The rays are generated by powerful 

 lamps and the milk must be exposed to this light in thin layers. 

 Under the most favorable conditions 99.9 per cent of the organ- 

 isms are destroyed. However, ultra-violet rays have not the same 

 selective action on pathogenic bacteria that heat has and the 

 process can hardly take the place of pasteurization. The factors 

 involved are more numerous than in pasteurization processes, 

 and are consequently more difficult to control under commercial 

 conditions. Vegetable cells succumb more easily than spores, 

 and the process is less suitable for cream than for milk, probably 

 because the viscosity causes it to flow in thicker layers. When 



