APPENDIX. 



L BACTERIOLOGIC EXAMINATION OF SOIL, 

 AIR, AND WATER. 



Although air and soil do not play the important role in 

 the transmission of disease assigned to them by the path- 

 ology of the past (pp. 169, 191), they nevertheless fre- 

 quently act as media for the transmission of disease-germs, 

 as has been shown in the preceding chapters. Bacterio- 

 scopic examination of air and soil is frequently demanded 

 of the hygienist when it is desired to determme the avail- 

 ability of ground for any public purpose. In individual 

 instances such examination may become the duty of the phy- 

 sician, when suspicion is aroused as to a relation between 

 existing disease and soil or air. Of much greater signifi- 

 cance in the development of the infectious diseases is water, 

 concerning whose essential participation in the causation 

 of epidemics reference has been made (pp. 170, 190). 

 Bacteriologic examination of water often devolves upon- the 

 physician. 



SOIL. 



Method of Investigation. By means of a sterilized 

 platinum spoon of known capacity (about -^ cu. cm.) a 

 specimen of the earth to be examined is taken up, and with 

 this Esmarch gelatin roll-tubes are made, in which subse- 

 quently the number of colonies that have developed a're 

 counted and their nature is determined with the aid of a 

 microscope. Ordinary plates may, likewise, be prepared. 

 In order that a portion of the fragments of earth shall not 

 remain behind in the test-tube when poured out, and the 

 result of the estimation be, thereby, rendered quite uncer- 

 tain, especial care must be taken to secure uniform distribu- 



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