CHEMICAL EXAMINATION 367 
The action of rennin is then proteolytic since it destroys casein. 
It might be regarded as a preliminary process in digestion, Bosworth 
(1913) states that probably the action attributed to rennin may be 
produced by any proteolytic enzyme. In the bacterial world this 
has been known for some time that an organism which will split casein 
will also probably split gelatin and other proteins. This is especially 
well borne out in the following table compiled by Frost and McCamp- 
bell and taken from their text. 
From this table one might infer that there was a specificity even for 
the different proteins. 
TABLE XXXIX 
ACTION OF CERTAIN BACTERIA ON CERTAIN PROTEINS 
(Frost and McCampbell) 
MILx. 
Name of Organism. nn nmnnnnnnernnt Gelatin. | Serum. AM ein. Fibrin. 
Coag. Digest. 
ss aeeenrmemeemnenena nian lnidiememmtiamepenimnmeennmnimemuamant Tenieiimensscnnneninieneemmmmeniiennntenn! Lipimmanmmemmnnmescamnanemeimmmmmm nen? tapihaneesmm mmm neta) Keteininemmiiiennaemtenemnenanaummmaied 
Bact. anthracis......... + 
Microspira comma....... + 
M. pyogenes aureus...... - 
Pseudomonas pyocyaneus. + 
Pseudomonas violacea.... _ 
Bacillus mycoides....... + 
Bacillus prodigiosus...... _ 
Aspergillus niger........ + 
Asnergillus oryz@........ ~ | ! 
b+ i++ 
+++) +44 
+l +++++4+4+ 
+ittititi 
+ 1+ 
| 
CHEMICAL EXAMINATION 
The functions of the chemical and bacteriological examinations may 
be entirely different although, in many cases, they must go along 
together. A sanitarian must have all the knowledge which it is pos- 
sible to secure and should not exclude either data if he would come to 
an accurate conclusion. In the chemical examinations that are made on 
milk, data may be secured with regard to the normal or abnormal occur- 
rence of any milk constituent. The presence of preservatives may be 
directly determined while, in the bacteriological examination, they may 
be indirectly inferred if the milk does not sour when it is placed in a 
favorable environment for this change. 
Sampling of Milk. To secure accurate results from the chemical 
or bacterial examination of milk requires good sampling. Too much 
