THE MICROSCOPE. 115 



barometric-indication of the general health or some particular dis- 

 turbance, and it is surprising how very fast they multiply while sim- 

 ply passing the intestines under circumstances favorable for their 

 growth. These forms, so small, are important, because so very 

 numerous, and their study has been perhaps avoided by many, yet 

 they certainly mean something and effect something, even the non- 

 malignant varieties as mentioned above, and it is certainly worth 

 while to continue to study their meaning, even beyond what has 

 already been written by others on the subject. 



J. M. ADAMS. 



Watertown, N. Y. 



THE HISTORY OF THE MICROSCOPE AND ITS ACCES- 

 SORIES. 



BY J. W. CRUMBAUGH, M. D. 

 THIRD PAPER. 



IN Dr. Henry Baker's microscopic essays (1753, London), we 

 find the first representation of them, and, so far as we know, 

 reproduced but once, and that by Queckett, in his popular article 

 on this subject. (To Ed — For diagram, see Queckett's work.) 



The following is a description of the diagram : The fiat 

 part, A, is composed of two silver plates, finely finished and 

 rivetted together at b-b, b-b, b-b. Between these, at c, there is set 

 a small bi-convex lens in a socket, with perforation of plates for eye 

 and light. Limb of silver at d is fastened to the plates by screw e, 

 which goes through both. Another part of this limb joined to it at 

 right angles passes under. The plate comes out on the other side. 

 Through this runs directly up a long, fine thread-screw, g^ which 

 raises or lowers the stage, h, whereon a coarse, rugged pin, /, for 

 the object to be fastened to, is turned about by a little handle, k. 

 The stage and pin are moved to and from the line by the little 

 screw, /. 



All parts were made of silver, highly polished. The lenses 

 were good, and those given to the Roy. Soc. of powers varying 

 from 40 to 160. His success was not due so much to the exceeding 

 excellence of his glasses as to his superior judgment. It is very 

 evident, from some of his discoveries, that he must have had lenses 



