278 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



or abundance of any special form or forms of cells and the 

 prevalence of any of these diseases. (6.) The amount of in- 

 organic and amorphous particles and other debris suspended 

 in the atmosphere is directly dependent on conditions of moist- 

 ure and of velocity of wind. 



These results on the part of Dr. Cunningham appear to 

 agree quite closely with those of Robin, but differ more from 

 those of Pouchet and Ehrenberg. In regard to the origin 

 of bacteria, the present experiments are not opposed to the 

 belief in the transmission of organisms by the atmosphere, 

 for they were actually observed among the particles in moist 

 air. In conclusion, Dr. Cunningham remarks that there are 

 many interesting questions which are suggested in connection 

 with the fact of the presence of such considerable numbers 

 of living cells in the air as he has found. What becomes of 

 them when drawn into the respiratory cavities of animals ? 

 Is their vitality destroyed; and, if so, how are they got rid 

 of? Are they capable of undergoing development within 

 the organism, and do they exert a prejudicial influence on the 

 recipient ? These and other similar questions, the author re- 

 marks, are only to be answered by means of patient and con- 

 tinued experiment. India Report. 



LIMIT IN THE AVAILABLE POWER OF MICROSCOPE LENSES. 



According to Professor Abbe, of Jena, the limit of capabili- 

 ty of a microscope,in showing the structure of tissues and the 

 character of minute objects, has nearly, if not entirely, been 

 reached, higher powers than those now in use giving rise to 

 optical phenomena which are likely to completely mask the 

 structure and character of the object under examination. 

 Thus it may happen that while different structures give the 

 same microscopical image, like structures will give different 

 images; and while systems of fine lines, and the like, may 

 appear ever so distinct and well marked in the microscope, 

 we are not entitled to regard such appearances as of morpho- 

 logical significance, but merely as physical phenomena from 

 which nothing can be inferred, except the presence of such 

 structural conditions as are capable of producing the diffrac- 

 tion effects obtained. 



These observations apply more especially to the marking 

 of certain diatoms and of striated muscular fibre. According 



