A Letter from Professor Abbe. 157 



Unlike many observers, Dr. Marvin hesitates to attach much 

 importance to their presence. The hepatic cells were granular 

 and often stained with bile, with many oil-globules surround- 

 ing them, showing fatty infiltration as well as degeneration. 

 Sections of the kidneys frequently showed tubal and inter- 

 tubal hemorrhages, and some indications of fatty degeneration. 

 "The disease is clearly dependent upon a specific blood-poison 

 as yet not demonstrated by the microscope, unless we regard 

 the changes found in the blood, as detailed above, as the cause 

 rather than a result of the disease. By adopting the theory 

 of specific blood-poisoning, the symptomatology of the dis- 

 ease is readily understood." 



No restrictions seem to have been imposed upon the em- 

 ployees of the hospital. People from the city paid frequent 

 visits to the wards. No clothing was burned or disinfected, 

 and yet, not one of these persons was troubled with the 

 disease. 



A LETTER FROM PROFESSOR ABBE. 



On page 30 of the paper " The Oil Immersion of Carl Zeiss Com- 

 pared, Etc.," in the first issue of this Journal, Prof. H. L. Smith 

 pronounces the objective tested by him to be a three-system objec- 

 tive, in opposition to the statement of Mr. Zeiss's circular. I hope 

 Prof. Smith will give credit to my assertion, that the objective in 

 question is, really, a four-system ; z. e., is composed of four separate 

 lenses, though, in his opinion, the . front lens may be too large for 

 any four-system combination of equivalent focus. 



Relative to the aperture of these objectives I beg to state, that 

 every standard >^ th or y^th made on this immersion plan by Mr. 

 Zeiss, will admit, and bring to an exact focus, rays of such an ob- 

 liquity that, the angle of the extreme ray with the axis being con- 

 sidered in the immersion-fluid, or in any other medium in front, the 

 sine of this angle multiplied by the index of this medium yields a 

 product equal to the number 1.26 to 1.27; which corresponds to a 

 balsam-angle of 114 to 116 degrees. 



But I must add, that in consequence of a mistake in the application 

 of my formulas, caused by me, several specimens of the y% th have 

 been made with a balsam-angle of 107 to 109 degrees only (not less). 

 This defect having been overlooked for a short time, some of these 

 lower-angled glasses have been sent away — two or three to England, 

 and one to America. From what Prof. Smith mentions about the 

 aperture of the objective, I infer that he has examined the lower- 

 angled y% th which was sent to Charlestown, near Boston. 



