1886.] 



MICROSCOPICAL JOURNAL. 



218 



r 



oleomargarine. We requested sev- 

 eral persons to taste these and pro- 

 nounce upon their relative merits, 

 and attempt to distinguish them by 

 the taste. The butter was universally 

 pronounced to be the inferior article, 

 and the experimenters, who had been 

 farm-bred boys, though they didn't 

 know oleomargarine by the taste or 

 look, judged that sample the better 

 article, and hence they concluded it 

 more likely to be butter. To the taste 

 it was butter, but under the micro- 

 scope there was a great difference 

 between the two. The butter sample 

 was destitute of fat crystals of any 

 sort, but the oleomargarine was largely 

 composed of two sorts of crvstals, re- 

 sembling the one fat and the other 

 krd. We do not wish to enter the 

 butter-crystal war, chiefly from lack 

 of sufficient time to investigate the 

 matter fully for ourself, but of the 

 value of this test for separating the 

 true from the false in the existing but- 

 ters we feel assured so far as we have 

 been able to inform ourself. 



Test of Watp:r Purificatio^n. — 

 A most interesting account of the 

 application of refined and delicate bi- 

 ological methods of investigation to 

 practical uses is given in an article by 

 P. F. Frankland, Ph. D., associate 

 of the Royal School of Mines, which 

 first appeared in the Proceedings of 

 the Institution of Civil Engineers, and 

 which we take from Van Nostrand's 

 Engineering Magazine for Oct., i8S6, 

 p. 316. In attempting the purifica- 

 tion of water for domestic uses, 

 there were found to be two sorts of in- 

 jury ; one which resulted from the 

 presence of large amounts of organic 

 matter in decomposing state ; this 

 could readily be detected by chemical 

 examination. A second where the ab- 

 solute amount of organic matter was 

 far below the injurious limit ; but 

 where there were present micro-or- 

 ganisms which, if introduced into the 

 body, might be the cause of contagion. 

 Chemical examination would be help- 

 less here, and yet the water really 



more dangerous than water which 

 might fail to pass the chemical tests. 

 Thus, in testing the value of various 

 methods of purifying water, the chem- 

 ical method alone would not be suf- 

 ficient. The culture method of Koch 

 is so simple in principle as to be 

 readily understood. The micro-or- 

 ganisms multiply so rapidly that from 

 one a vast number soon descends. If 

 the organisms be reared in a fluid me- 

 dium, where the conditions for rapid 

 growth are furnished, it is impossible 

 to infer from the number present how 

 many were present to begin with. 

 But if the organisms be distributed 

 through a medium suitable for their 

 multiplication, and then deprived of 

 the power of movement, the number 

 of colonies arising from the multipli- 

 cation of these isolated individuals in- 

 dicates the number of organisms intro- 

 duced. Koch complied with these con- 

 ditions by introducing gelatin in his 

 culture medium, and this medium, with 

 the sample of water mixed through 

 it, spread out upon a glass slide and 

 left to develop under a glass cover. 

 The imprisoned organisms, growing 

 rapidly, form thus isolated colonies, 

 which may be readily recognized by 

 the naked eye or with a low magnifying 

 power, and give a ready means of 

 determining their abundance in the 

 water to be tested. Until the 

 method of water examination by gel- 

 atin culture was devised, there were 

 no available means by which the rel- 

 ative efficiency for the removal of 

 micro-organisms of difterent filtering 

 materials could be estimated upon a 

 quantitative basis. 



o 



Seaside Laboratories. — Every 

 reader of the jfoui'iial^ who has not 

 already done so, will please and in- 

 struct himself by consulting two ar- 

 ticles which have recently appeared 

 upon zoological marine laboratories. 

 One is the description, by Mrs. Whit- 

 man, of Dohrn's Zoological Station 

 at Naples, a valuable account of which 

 appeared in the October Century 

 Magazine. Mrs. Whitman, besides 



