2404 Journal of Applied Microscopy 



The agar was then poured into sterile Petri dishes, where it solidified. . . It 

 is reasonable to suppose that if bacteria were present on the flies, some of them, 

 at least, would be washed off by this process into the agar, where they would 

 multiply and form colonies." 



The dishes obtained from these experiments varied greatly, but all of them 

 developed colonies, the number ranging from fifty to over two thousand. " Flies 

 ill nature, '' they conclude, therefore, "probably always do cany bacteria with 

 them.'''' 



" From the standpoint of public hygiene," they continue, " these conclusions 

 are very significant; for, admitting that flies can carry harmless bacteria, there 

 seems to be no reason why they cannot carry disease-producing bacteria as well. 

 In fact, it has been a general belief among scientists for a number of years that 

 they are active agents in the transmission of many diseases. Recent studies by 

 Dr. L. O. Howard on the breeding habits of these insects furnish good evidence 

 that they occasionally play an important role in the transmission of typhoid fever. 

 It is probable that they can, and do, carry the germs of any disease that offers 

 them an opportunity to come in contact with infected material." 



" Their work is of value," says School Science, " not only on account of its 

 scientific interest, but, also, because it points the way to a new field of effort open 

 to secondary students, — a field whose development would have an important 

 influence on educational methods, as well as on public health problems." 

 Johns Hopkins University. W. H. Manwaring. 



Preparations for Dissecting Pans. 



In view of the fact that such preparations for dissecting pans, as are on the 

 market at present, are either expensive or not very serviceable, or both, it was 

 thought worth while to attempt to work up some mixture that would be more 

 serviceable and less expensive. 



An ideal preparation for dissecting pans, it seems to me, should be of such a 

 nature that it will hold the pins. It should be soft enough so as not to crack 

 when bent, adhesive enough to stick to the pans, black enough to form a sharp 

 contrast with delicate tissues, and insoluble in solutions (water, 70 per cent, 

 alcohol, and formal) commonly used in dissection. 



After considerable experimenting, two preparations were obtained, neither of 

 which prove to be ideal. The formulae of these two preparations (A and B) are as 

 follows : 



Preparation A. Preparation B. 



25 grams of Linseed oil, 50 grams of Coal tar, 



50 " " Coal tar, 100 " " Brown resin, 



200 " " Brown resin, 250 " " Hard paraffin. 



50 " " Hard paraffin. 



The ingredients of preparation (A) mix most readily if all but the paraffin is 

 first melted and thoroughly mixed, and then the paraffin added and melted and 

 the whole thoroughly stirred. This preparation may be made harder by con- 



