Journal of Applied Microscopy. 



209 



the udder. Samples of milk were col- 

 lected in sterile test-tubes as it welled 

 out of the cistern and its smaller rami- 

 fications. In making cultures from the 

 glandular tissue, care was taken to pre- 

 vent milk of the ventral region from 

 coming in contact with the freshly ex- 

 posed surfaces. Bits of tissue were 

 detached with flamed scissors, and trans- 

 ferred to culture media by the use of a 

 flamed platinum loop. Tubes of gelatin 

 and of agar were inoculated in this man- 

 ner from each of the three arbitrarily 

 designated divisions of the quarter. The 

 same procedure was repeated with each 

 of the other three quarters of the udder. 

 Cultures were made from the udders of 

 six cows in the manner described. 



Upon returning to the laboratory the 

 gelatin was liquefied at a temperature 

 not exceeding 37 degrees C and poured 

 into sterile Petri dishes, where it again 

 became solid. Agar plate cultures were 

 made from the milk samples, and, to- 

 gether with those slanted agar cultures 

 already inoculated, were placed in the 

 incubator. The agar plate cultures were 

 designed to be used as a check upon the 

 reliability of the conclusions reached 

 from an examination of the other cul- 

 tures. For instance: it might be possible 

 that organisms appearing to have been 

 obtained from the interior of the udder 

 may have lodged upon the bits of tissue 

 during the transfer. The identity in cul- 

 tural and morphologic characters of bac- 

 teria found in cultures made from the 

 fore milk and the glandular tissue of the 

 udder would eliminate a source for false 

 conclusions. 



The tubes of slanted agar, after stand- 

 ing in the incubator for several days 

 were examined particularly with refer- 

 ence to the presence or absence of 

 growth. Nearly all of the media which 

 had been in contact with material from 

 the udder showed growth. Note was 

 taken of the color and character of the 

 growth of the colonies and sub-cultures 

 were made. 



The gelatin plate cultures were in like 

 manner examined, furnishing a more sat- 

 isfactory method for obtaining pure cul- 

 tures. With these, a direct comparison 

 made it possible to trace the presence of 

 the same organism in the three localities. 

 In order to prove that these identities 

 existed, sub-cultures were made for a 

 more detailed comparison later. The 

 plate cultures made from the milk were 

 examined and sub-cultures were made 

 from all of the apparently different colo- 

 nies. 



By comparing cultures from the various 

 sources, it was found that the same or- 

 ganism frequently occurred in the fore 

 milk an-^ in each of the three parts of the 

 udder. (See illustration.) Most of the 

 bacteria obtained in pure cultures were 



found to belong to one of three species 

 of micrococci. Cultures of the three 

 species were obtained from a sufficient 

 variety of sources to demonstrate their 

 general distribution throughout the 

 udder. 



The apparently healthy udders of six 

 milch cows were in that manner found to 

 contain bacteria in the depths of the milk 

 secreting tissue. By the methods 

 employed, it was impossible to detect any 

 difference in the relative numbers of bac- 

 teria present in the three regions of the 

 udder. 



The evidence at hand indicates that the 

 teats and the greater portion of the udder 

 may normally contain bacteria. It also 

 seems highly probable that a few at least 

 of the organisms found in the udder 

 remain there after each milking, becom- 

 ing the progenitors of the organisms 

 found to be present in the milk when 

 drawn. This conclusion seems to be sup- 

 ported by the following facts: 



1. Certain species of bacteria have 

 been found to persist in particular quar- 

 ters of the udder for considerable periods 

 of time. This controverts the statement 

 that the milk ducts are sterile at the 

 close of the milking, becoming tenanted 

 from the outside by any organisms which 

 by chance come in contact with the end 

 of the duct. 



2. It is possible for bacteria to remain 

 in the udder and not be ejected along 

 with the milk. This has been proven 

 possible in the case of one organism. A 

 culture of Bacillus prodigiosus has been 

 introduced into the milk cistern and has 

 succeeded in persisting there for six days, 

 as was shown by its presence for that 

 period in the milk of that quarter of the 

 udder. 



3. Cultures of bacteria have been 

 obtained by Dr. Moore and the writer 

 from the glandular tissue of the udders 

 of freshly killed milch cows. Identical 

 species of micrococci were obtained from 

 the milk and from the glandular tissue 

 of the udder. 



4. It has not been shown by the investi- 

 gations published up to this time that the 

 last milk drawn is always sterile. 



Archibald R. Ward. 

 From the laboratory of Comparative 

 Pathology and Bacteriology, New York 

 State Veterinary College, Cornell Uni- 

 versity, Ithaca, N. Y. 



Centrifugal Milk Analysis. 



For most practical purposes the butter 

 fat is the only component of milk which 

 it is necessary to determine quantitative- 

 ly. The fat is the most important milk 

 component from a commercial point of 

 view, and in human nutrition it is the 

 best index to the food value of the milk. 



