2i 4 THE MICROSCOPE. 



smeared upon the same garment or a similar fabric, restored by the 

 same solutions, and treated, in every respect like the specimen to be 

 identified. 



You will readily discover the following facts: The human red 

 corpuscles will average much larger than those of any dog. You 

 will find some larger corpuscles in the dog's blood, and some smaller 

 ones, too, than the average corpuscle in human blood. But, the 

 largest corpuscle of the dog will rarely, if ever, be found as large as 

 the largest of man, while the smallest will average smaller than the 

 smallest of man. 



You will also note that the cell-wall of the human corpuscle is 

 much thinner than that of the dog and that the expansibility of the 

 human corpuscle — when treated with pure water, instead of the 

 saline solution— is much greater than that found in the corpuscle of 

 the dog. 



The human corpuscle will expand to the rupturing point and 

 collapse much sooner than will that of the dog, when treated pre- 

 cisely alike. 



Measuring the cell-walls of perfect corpuscles in man and dog, 

 you will readily perceive that the latter is perceptably thicker than 

 that of the former and that the corpuscle of the dog exhibits a 

 peculiar toughness of cell-wall, difficult to describe yet always 

 recognizable to those much given to their investigation. 



Again, mounting three or more slides dry in balsam, from the 

 specimen to be identified, and from your known specimens of dog 

 and human blood — prepared and mounted precisely alike — upon 

 very thin cover-glasses, place them under your solar microscope,! 

 and, by means of a. T *j or y 1 ^ objective, project thein, 6 or 8 feet 

 distance, upon a tightly stretched screen, in your dark room. Apply 

 to these images upon the screen, a glass rule, divided into spaces of 

 about -Jj of an inch when the difference in size of the corpuscles 

 will become still more manifest by reason of the greater amplifica- 

 tion while the cell-walls of the dog corpuscles will be seen to cast a 

 heavier shadow than those of man. 



"Where is the exact size to judge by?" 



In reply, there is no exact size, nor is any needed, save that 



+1 use the Mcintosh solar projecting apparatus, the same as exhibited in Chicago, at the 

 annua! meeting. The oxy-hydrogen light does not make the outlines sufficiently plain to per- 

 mit of accurate measurements. 



