56 



THE AMERICAN MONTHLY 



[March, 



was still perfect; and says, 'the 

 shellac is entirely unnecessary and 

 indeed an injury. The fluid zinc, 

 properly made, is all sufficient.' 

 Wax cells cei'tainly do stand remark- 

 ably well, but we do not favor them 

 so much as we did a few years back, 

 for there is almost certain to be a de- 

 posit on the cover-glass after a time. 



This statement controverts certain 

 others that we have made in the past 

 concerning this subject, for we have 

 repeatedly said that; in none of our 

 own mounts with wax has such a 

 deposit occurred. The mounts re- 

 ferred to were all several years old — 

 four or five at least — and we felt tol- 

 erably sure that during that time they 

 would have shown all imperfections 

 that would likely develop. Within 

 a year, however, in the climate of 

 Washington, we have observed a dis- 

 position toward a clouding of the 

 covers from condensation of some- 

 thing on the under surface. Hitherto 

 we have supposed this defect due to the 

 manner of mounting, perhaps from 

 imperfect drying of the specimen, or 

 possibly from the cement. It appears, 

 however, to come from the w a x 

 itself. 



A paragraph is devoted to white 

 zinc cement, which gives us consid- 

 erable satisfaction in view of the 

 round abuse we have received from 

 various quarters for stating the re- 

 sults of our observations concerning 

 the value of this cement, for all we 

 have said is confirmed in a most 

 unquestionable manner. The ex- 

 perience of the Club at large is of far 

 more value than individual preju- 

 dices in a matter of this kind. Let 

 the reader consider that we refer not 

 to what may be done with this ce- 

 ment, but to what is done with it by 

 many who use it. 



Dr. Ward says that ^ curtain-ring 

 mounts regularly go to pieces in the 

 circuits.' This, we believe, need 

 not be. Curtain-rings are exceed- 

 ingly useful in mounting, and it will 

 be a pity if we must give them up. 

 Certainly they can be securely at- 



tached to the glass. Cannot some 

 reader give some valuable experience 

 in this matter? 



Micro-organisms of Milk. — 

 Herr F. Hueppe has studied* the 

 various micro-organisms which de- 

 velop in milk, cultivating them on 

 gelatin by Koch's method. In the 

 early stage of souring, when the 

 milk curdles, if a needle be dipped 

 into it and drawn over a prepared 

 gelatin surface, in the course of two 

 days fine white points of growth 

 will be observed. Pure cultures 

 obtained in the usual manner from 

 these reveal the presence of several 

 distinct species, but the true bacillus 

 of fermentation of milk has been 

 isolated and followed through nu- 

 merous successive cviltures. The 

 individuals, stained with anilin colors 

 and observed with an oil-immersion 

 lens appear as plump rods, 1-1.7// 

 in length by 0.3-0.4,'x in diameter. 

 They seem to be motionless during 

 life. The bacillus develops slowly 

 at a temperature of io°-i2° C, 

 i-eaches a maximum between 35° and 

 42° C, and ceases to grow, losing also 

 its specific eflect, at about 45°. 



A micrococcus is also abundant in 

 the gelatin culture taken from the 

 milk in the manner above described. 

 It has been shown, however, that 

 this organism does not produce lactic 

 fermentation. 



It has already been observed by 

 others and confirmed by the author, 

 that milk which is prevented from 

 undergoing lactic fermentation may, 

 nevertheless, become curdled, and 

 later manifest an alkaline reaction. 

 In such cases the author has inva- 

 riably found only large bacilli, which 

 must undoubtedly be regarded as the 

 butyric acid ferment. 



The organism of blue milk obtained 

 by gelatin cultures is also a motion- 

 less bacillus, which in the original 

 gelatin culture is readily distin- 

 guished by its color, at first yellow- 



* Zeitsch. fur Mikroskopie , ii, no. 



