THE MICROSCOPE IN DIAGNOSIS. 299 



that cholesterin or nerve-fat may be seen in blood which 

 has been kept from one to three days, and that variations 

 in this, seen under the microscope, may throw light upon 

 disordered mental and nervous functions. He claims that 

 carbuncle, intermittent fever, enteric fever, and small-pox 

 are produced by fungi in the blood, which he names re- 

 spectively Crypta carbunculata, Gemiasma viridis, Byoly- 

 sis typhoides, and Ivy variolosa. 



The examination of blood in disease requires patient 

 care and the employment of high powers, not less than 

 1000 diameters. As a field for original investigation, this 

 subject affords a most tempting opportunity to those who 

 have the leisure and skill to pursue it. The time may 

 come when more may be known of a patient's disease by 

 an examination of a drop of blood under the microscope 

 than is possible in any other way. 



In medico-legal inquiries the decision whether a blood- 

 stain is of human blood or of one of the lower animals is 

 one requiring exceptional skill, if, indeed, it is at all 

 practicable. The differences given on page 187 are easily 

 enough seen, but the red disks in a dog, a rabbit, etc., so 

 nearly approach those of human blood in size, and the 

 appearance of corpuscles in the same drop varies so much 

 under high powers, as to lead to doubtful testimony before 

 a jury. Dr. J. G. Richardson believes it quite possible to 

 distinguish human blood, but at present few microscopists 

 agree with him. In a doubtful case it would be well to 

 scrape off from the slide half of the drop of suspected 

 blood, replace it with undoubted human blood, and pho- 

 tograph the disks, so that one-half in the field of view 

 would be known and ready for comparison with the other 

 half. 



To detect the red corpuscles in a blood-stain, it is well 

 to soften the clot with glycerin diluted with water to the 

 specific gravity of serum, or a one per cent, solution of 

 salt may be used. If this fails, an attempt may be made 



