516 



SCIENCE 



[N. S. Vol. XXXIV. No. 877 



water than was present before filtration." 

 These remarks are especially applicable to so- 

 called gravity filters in which the filtering 

 material is composed of vegetable or animal 

 charcoal, sand, spongy iron, magnetic carbide 

 of iron, polarite and carferal, the latter sub- 

 stance being a mixture of iron, charcoal and 

 clay. It should be distinctly understood that 

 there is no such a thing as a self-cleaning 

 filter and even the Pasteur-Chamberland, 

 Berkefeld and filters of the type in which the 

 water is passed under pressure through hollow 

 porous porcelain cylinders require periodical 

 cleaning at short intervals by a hard brush — ■ 

 otherwise bacteria may in time grow through 

 the cylinder and appear in the efiiuent; while 

 it has been shown by Dr. Horrocks that the 

 typhoid organisms are not able to grow 

 through the walls of the Pasteur-Chamberland 

 candle, they can grow through the walls of the 

 Berkefeld candles " probably owing to the 

 larger size of the lacunar spaces " and hence 

 the Berkefeld candles should be sterilized in 

 boiling water every third day. On the whole, 

 we may conclude that it is clearly the duty of 

 every community to supply a pure wholesome 

 water, so that domestic filtration may not be 

 necessary. 



Among the diseases believed to be produced 

 by impure water the authors refer especially 

 to dyspepsia, dysentery and diarrhcea, typhoid 

 fever, cholera and a number of entozoal infec- 

 tions. The relations of water to goiter and 

 cretinism require further researches. In yel- 

 low fever, diphtheria, urinary calculi and 

 rickets, formerly believed to be influenced by 

 the drinking water, the evidence is so indefi- 

 nite that the water theory has been generally 

 abandoned. Recent observations by Schroe- 

 der, of the Department of Agriculture, and 

 others indicate that the germs of tuberculosis 

 are frequently present in the alvine discharges 

 of tuberculous animals and man and by sew- 

 age pollution may thus infect the water 

 supply. 



Every sanitarian will heartily endorse the 

 authors' chapter on the collection, removal 

 and disposal of excretal and other refuse, be- 

 cause " the public health largely depends on 



the efiiciency with which refuse matters and 

 especially human excretal refuse, are removed 

 from towns; the health of towns in this coun- 

 try and abroad has very much improved, and 

 the death rates have been permanently low- 

 ered, as the results of works of sewerage. . . . 

 The pail system is undoubtedly the best for 

 towns which will not enforce the adoption of 

 water closets. In the case of Nottingham, 

 where middens, pails and water-closets are in 

 use iu different parts of the town. Dr. Bool- 

 byer has shown that the greatest prevalence 

 of enteric (typhoid) fever is to be found in 

 the houses with middens, and the least in the 

 water-closeted houses, those with pails occupy- 

 ing an intermediate position." 



The chapter on Air and Ventilation deals 

 very fully with this important subject. Re- 

 cent researches clearly reveal that neither an 

 excess of CO, or a deficiency of oxygen were 

 responsible for the effects of so-called vitiated 

 air so long as the temperature and humidity 

 of the air were kept low. As soon as the tem- 

 perature and humidity were increased beyond 

 certain limits there appeared, both in normal 

 and in diseased persons who were submitted 

 to experiment, the usual symptoms that occur 

 when people are crowded together in one room 

 — " i. e., feelings of drowsiness and headache, 

 oppression, lassitude, giddiness, nausea, etc. 

 These symptoms, however, could be relieved at 

 once simply by reducing the temperature and 

 humidity of the air to normal and they may 

 be attributable to heat retention." 



In summing up the discussion the authors 

 suggest the importance of " additional re- 

 search to ascertain the organic constituents 

 (if any) of expired air and to differentiate 

 them from the volatile products of decomposi- 

 tion arising from the general surface and 

 other parts of the body. ... It may, however, 

 be the fact that whilst nothing of any impor- 

 tance is given off to the air by human respira- 

 tion and transpiration, yet the air by such 

 means is deprived of some vital element, with 

 which we are unacquainted, and without 

 which the highest state of bodily health and 

 efiiciency can not be maintained." 



The causal relation of impure air to so- 



