TEACHING OF PHYSIOLOGY AND PUBLIC HEALTH. 37 



to some person, there to set going the various forms of 

 gastric or intestinal tuberculosis. 



In such a brief account we are not specially concerned 

 with the question what bacteria are. Suffice it to say that 

 they are minute organisms, among the smallest known. 

 Several typical forms are usually described. Thus the little 

 round globular form, such as the germ that causes erysip- 

 elas, is called micro-cocczis. The short rod-like form, such 

 as the one that induces the decomposition of flesh, is called 

 bacterium. (Used in this instance in a special way and not 

 referring to the whole group.) Longer rod-like forms are 

 represented by the germs of consumption, typhoid fever, 

 leprosy, lockjaw, etc., and are called bacilli. The comma 

 bacillus of Asiatic cholera has a slightly bent shape not 

 unlike the comma, whence its name, and belongs to the 

 order of the vibrios. In typhus recurrent fever occurs 

 the cork -screw -like form called spiro-chaeta, while the 

 undulating snake-like form frequently found in the mouth 

 and the teeth, is called spirillum. In addition to the 

 active forms most bacteria are able to produce, when the 

 necessity arises, spores which are able to resist drought or 

 any other unfavorable circumstance for a long time, only to 

 germinate again as soon as proper conditions arise. The 

 resistance of some of these spores is almost incredible. 

 The spores of the hay bacillus, found in ordinary hay, may 

 be boiled several minutes without injuring their vitality. 

 Spores may be formed either by the protoplasm of a bac- 

 terium forming a thick wall around itself for extra protec- 

 tion, or by the protoplasmic contents of a bacillus splitting 

 up into several small globular bodies which are soon pro- 

 vided with a thick coat, and in this form mingle with the 

 dust of the atmosphere to be wafted and scattered by every 

 breeze that stirs. 



But it must not be supposed that all germs are disease- 

 producing. Many of them are of the utmost benefit to us. 

 The germs that cause the ordinary decomposition of organic 

 matter by returning it to the elements, keep things clean 



