14 MASS. EXPERIMENT STATION BULLETIN 293 



carried out in cooperation with the Department of Botany. The results of the 

 experiments have been published {Soil Science 34:337-351, 1932), and reference 

 may be made to the published paper for details of the study. 



Application of the Soil Plaque Method for Determining Mineral Defi- 

 ciencies in Massachusetts Soils. (J. E. Fuller.) The method depends on the 

 growth of Azotobacter as an indicator of the presence in the soil of minerals essen- 

 tial to the growth of crops. The results obtained from the soils studied indicated 

 that the method cannot be depended upon for determining the deficiency of avail- 

 able phosphorus under the conditions existing in the field from which the samples 

 were taken. It was observed that the soils did not contain sufficient phosphorus 

 to support Azotobacter growth, even though the field from which the samples 

 were taken had produced satisfactory crops. Further studies are being made with 

 soil samples collected from more widely distributed areas. 



Bacteriological Studies of Dried Milk Powders. (J. E. Fuller and R. L. 

 France.) Several samples of dried milk powder were examined for the presence 

 of the tubercle bacillus in order to determine the safety of the pow-der for feeding 

 calves. Some of the samples were from milk powder dried by the roller process; 

 others, from milk powder dried by the spray process. The latter, being easily 

 soluble in water, were made into solution and inoculated into guinea pigs. The 

 animals of this group were observed for a month and then killed. The milk powder 

 dried by the roller process was only partially soluble in water, so the powder was 

 mixed with other food and fed to guinea pigs. The animals of this group were 

 observed for two months and then killed. Both groups of guinea pigs appeared 

 to be healthy throughout the periods of observation. The weights of all of the ani- 

 mals showed gradual increase. Autopsies did not show any evidence of tubercular 

 infection in any of the animals. The experiments indicated that the milk powders 

 studied did not contain tubercle bacilli. These results agreed w ith those obtained 

 by other investigators. 



Udder Infection in a Cow. (J. E. P'uller and R. L. France.) The udder 

 infection studied occurred in a cow of the experiment station herd. An organism 

 was isolated from the milk and also from the udder when the cow was killed. 



The blood serum of the cow agglutinated the organism to a titer of 1 to 

 1,280. The study will be reported more in detail at a later date. 



Laboratory Service. (R. L. France.) Following is a list of the number and 

 types of examinations made by the laboratory during the past year: 



Milk (bacteria counts) 1,160 



Water analysis < 123 



Miscellaneous: 



*Butter fat 197 



*Milk solids 7 



Baby foods 12 



Throat swabs 10 



Chlorine 4 



^'east 2 



Powdered milk 1 



Anaerobes 1 



Food poisoning 1 



TOTAI 1,518 



♦Analysis made by P. H. Smith, Feed Control Laboratory. 



