MEDICAL WORK WITH MICROSCOPE 



vessels under a fairly high power. We shall find 

 that there are large and small vessels in his webbed 

 foot; we will devote our observation to the small 

 vessels, called capilliaries, from the Latin Capillus, 

 a hair, because of their small size. Probably the 

 blood will not flow when we make our first examina- 

 tion and this points to one of two things, either 

 the frog is bound too tightly or he has not recovered 

 from the alarm he experienced at his treatment. 

 In the latter event he will not be long recovering 

 and his blood circulation will soon be in full working 

 order; in the former case, we must loosen his 

 bandages. In some of the very small blood-vessels 

 we shall notice that the blood always flows in one 

 direction, in others it does not appear to have any 

 definite direction. In either case, however, we can 

 see the red corpuscles flowing rapidly along the 

 central stream of the blood-vessel whilst the white 

 corpuscles travel much more slowly along the sides. 

 The medical man may be called upon to decide 

 two questions concerning human blood; he may 

 wish to know whether it is healthy and, in the case 

 of certain crimes, he must be able to state positively 

 whether certain stains are caused by human blood 

 or not. Dealing with these questions in order, let 

 us see how we would proceed. There are many 

 people, far too many in towns who are described 

 as bloodless, the expression is of course an exag- 

 geration for no bloodless person could continue to 

 exist. What really happens is that such people are 

 deficient in red blood corpuscles. If we examine 



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