268 THE AMERICAN MONTHLY. [Sept. 



the study of membranes. This is especially applicable 

 when the fixation is by alcohol or by the bichromate. 

 When osmic acid is used, the piece of skin being very 

 small and the action of the fixative rapid, there is no 

 need of observing those conditions. We should here re- 

 peat what has been so often said, that the skin should 

 be perfectly fresh, if possible the result of an operation. 

 It should be taken from different parts of the body so as 

 to observe the modifications presented by the layers 

 composing it. 



To he Continued. 



The Use of Filtered Water in Microscopic Manipulation. 



By ARTHUR M. EDWARDS, M. D., 



NEWARK, N. J. 



I always use filtered water in microscopic manipula- 

 tions, for filtered water is better then distilled water. 

 We may use distilled water and introduce minute organ- 

 isms into the field which will thereafter become extremely 

 puzzling and mar the investigation irretrievably. These 

 may be introduced in the funnel or vessels used. But 

 if the funnel and vessels are wiped dry before using, of 

 course there is not a danger of introducing extraneous 

 substa,nces. I find that if water for washing is used im- 

 mediately it is best; for spontaneous generation, if it be 

 present, seeds or eggs, cannot have time to develop. Mr. 

 Kitton some time ago noticed that water passed through 

 a filter developed Bacillariaceae if permitted to stand. 



In washing infusorial earths that contain spicules of 

 sponges, Foramenifera, E-adioiaria or Bacillariacese, the 

 calcareous of silicious organisms must be eliminated. 

 The Foramenifera being calcareous are difficult to keep 

 clear and must be viewed separately by the microscope. 

 But we have to use filtered water to prevent the minute 

 organisms present in all other water from being intro- 



