156 THE AMERICAN MONTHLY [May, 



icable diseases. The Board lias entered ui)on a most important 

 work for the prevention and restriction of tuberculosis in man, 

 and it is believed that the results will be great. This Board has 

 taken the lead of others in declaring consumption to be dan- 

 gerous to the public health, and has recommended advanced 

 measures for its restriction. 



Last year a useful Conference was held with special reference 

 to cholera. That subject is still of interest and dangerous im- 

 migrants are still coming into Michigan. But it is prop'sed 

 this year to give special attention to that disease which is al- 

 ready here and causes most deaths — consumption, and to give 

 the health officers opportunity to study the subject at the State 

 Laboratory of Hygiene where the bacteriological and other facts 

 relative to the causation of this disease can be so well demon- 

 strated. 



mCROSCOPICAL APPARATUS. 



A New 1-5 Objective. — In examining an object while still 

 in the compressor, such as I described in the last number of this 

 Journal, having glasses of 1-10 inch in thickness, one is natur- 

 ally restricted to objectives of low power. In my special work, 

 however, it was quite important that a higher power shoald be 

 occasionall}' used, and I made inquiry with negative results of 

 all the leading makers, for a 1-5 that would work through a 1-10 

 inch cover. I found that such an objective was not on the mar- 

 ket, but Messrs. Spencer and Smith of Buffalo, N. Y., offered to 

 design and make such an objective, and having received per- 

 mission from the U. S. Bureau of Animal Industry to give the 

 order, I received later on an objectiye, which was claimed by 

 the maker to give the results required. 



I find this 1-5 objective of 50° air angle, has very fine defini- 

 tion, tlie correction for the abnormally thick cover being per- 

 fect, but it will not work with ordinary glass covers, it being 

 impossible to make such a lens without collar adjustment. 



The use of glasses 1-10 of an inch thick, allowing great pres- 

 sure to be made, and sustained in a compressor frame, having 

 a screw adjustment at each end, has a wide field of usefulness, 

 and as the object can now be examined while under this com- 

 pression with as high a power as one-fifth, it opens new and 



