MEMOIRS OF TIIK NATIONAL ACADP:MY OF SCIENCES. 421 



for 1802, and iiichuliiii;' a paper l>y Dr. Theobald Smith, entitled -'A new method for determining 

 (luantitatively the poilntion of water by fa'eal bacteria,"' and also to I>r. Smitli's |)aper on '-The 

 fermentation tube," in the ^Vi]der (i>iiarter Century Kook, Ithaca, ISii:;. 



Tbei'e is no evid<'uco that a lew hundred or even a few Ihousand <if tiie urdinary Ibrms of the 

 eolou hacllli found in the excreta of healthy animals, or in river water, produce any special 

 patliological efleets when swallowed l)y men. Like the typhoid bacilli, they vary greatly iu 

 virulence — that is, in the power to produce disease — and this virulence a])pears to be much 

 increased iu certain diseases of the intestinal tract. Millions of them always exist iu the lower 

 part of the alimentary canal, and their imi)ortance in a water sui)ply, from a sauitary point of 

 view, depeuds uot so much ujion the risk of their producing disease by themselves as upon their 

 associatious with aud relations to the bacillus of typhoid. It is possible that the typhoid bacillus 

 is only a variety of the colon bacillus, which under certain circumstances inay be transformed 

 into it; but at present the majority of bacteriologists lielieve them to be distinct species. When 

 the colon bacilli are found in a well water it usually lndi(;ates contamination of the well by 

 washings from the surface; when found in a river water they may indicate either a recent rainfall 

 bringing in the surface washing of the watershed, contannnation by the droppings of animals, 

 or pollution by sewage containing human excreta, which last is the specially dangerous form of 

 pollution. 



The number of bacteria in river water depends much upon the rainfall, and is usually lowest 

 in summer when the rainfall is least; but this depends upon the character of the surface of the 

 drainage area — that is, as to the ])roportion which is wooded, rocky, cultivated, etc. The duration 

 of life, or the rapidity of multiplication of many species, appears to be small in flowing water, but 

 iu a sample collected iu a bottle the uudti[)]ication is rapid for several days, and hence it is 

 important to test the sample as soon as possible after it is collected. The differences in vitality 

 between the bacteria iu a flowing stream and in a closed vessel arei)robably due in part to the 

 influence of light, and especially of direct sunlight, which lias a powerful influence in killing 

 bacteria. 



Bacteria which will not grow at 37° or 38° C. will not grow iu the human body; but occa- 

 sionally some of these water bacteria, growing only at lower temperatures and which are not in 

 themselves pathogenic, may become important in a municipal water supply by producing acids 

 which will cause the water to attack lead service pipes to a dangerous extent. 



Returning now to the report of Dr. Wright, I wish to call attention to its value as a 

 contiibuti(Hi to the means of identification of different species or varieties of the bacteria found 

 in river waters. This value dei)ends in part upon the care with which the descriptions of the 

 peculiarities of each supposed species have been given aud in jtart upon the careful colored 

 drawings of the appearances presented by the colonies of those forms which could not be identified 

 from the descriptions of previous writers. Such drawings arc often more useful than many pages 

 of description, and it is extremely desirable that they sbould be made and published for all 

 supposed new species. Photographs are desirable, but such colored drawings as Dr. Wright has 

 made are needed also. 



He describes two species of micrococci, two of cladothrix, and forty-five of bacilli, besides 

 three varieties of the latter, making a total of flfty-two, nearly all coming from the Schuylkill 

 water. It is quite certain that this water contained other forms which he did not detect. The 

 great majority of them he could uot identify with any of the bacteria previously desciibed, and to 

 these he has given specific names. ]\Iany of them are chromogenic under certain circumstances, 

 and only three or four of them are itathogenic in animals. 



It will be seen from his charts that the greatest number of bacteria were found in January in 

 the Schuylkdl water, and in November, January, aud July in the Delaware water. There aijpears 

 to be no relation between the number of bacteria and the number of cases of typhoid fever, or the 

 amount of nitrates and of albuminoid ammoina, and but a slight relation between the proportion 

 of cases of typhoid and the amount of fiee or of albuminoid aninujnia. 



