§60 The Microscope. 



the outside or the inside of the cells. Another sound onion 

 from the grocery, never frozen, from which I cut a section a 

 ■week ago, has dead, separated protoplasm in the cells of a sec- 

 tion which I now make, a long distance from where I plugged it 

 for the former section. Such sections as I first described are 

 not readily obtained ; I found only a few among a great num- 

 ber of trials. I am now placing a number of bulbs in shallow 

 dishes of water, hoping to meet with more uniform success. 

 Planting in soil in boxes would be a still more promising method 

 of preparation. 



FLOATING PARTICLES IN THE EYE, A SOURCE OF 

 ERROR IN MICROSCOPICAL OBSERVATION. 



LUCIEN HOWE, M. D., P. R. M. S. 

 READ BEFORE THE AM. MICROS. SCO. 



AT THE meeting of the American Societ}^ of Microscopists 

 held at Cleveland, I had the honor of demonstrating the 

 fact that irregularity in the curvature of the cornea, which is 

 almost constantly present in the human eye, interferes materially 

 with certain microscopical work. This irregularity, known 

 technically as astigmatism, frequently prevents one person from 

 seeing fine lines, for example, those of the Nobert plate, or Dia- 

 tom striae, when these are placed in one direction, but they may 

 be seen by another person in that position, or indeed by the 

 same individual, if the position of the lines be somewhat altered. 

 It was gratifying to see that the subject was of suflficient value 

 to call forth one or two other articles in microscopical journals, 

 corroborating the observation, and I think there is now no doubt 

 that the existence of astigmatism must be regarded as a decided 

 obstacle to the proper observation of certain tests by individuals 

 who possess this peculiarity in any decided degree, and observa- 

 tion shows that in 96 or 98 per cent, this condition exists in a 

 sufficient degree t9 be measured by a suitable instrument, called 

 the ophthalmometer. 



In the present short paper I wish to call attention to the fact 

 that there exists in the ej^es of almost ever}'^ individual still 

 another imperfection sufficient to cause a faulty observation, 

 when looking at another class of objects. 



