116 THE BLOOD. 



lations be carefully conducted, the corpuscles may be recog- 

 nized without difficulty by the microscope. 1 



If pure water be added to a specimen of blood under the 

 microscope, the corpuscles will first swell up, become spher- 

 ical, and are finally lost to view by solution. The same effect 

 follows almost instantaneously on the addition of acetic acid. 



Structure. The structure of the blood-corpuscles is very 

 simple. They are perfectly homogeneous, presenting, in 

 their normal condition, no nuclei nor granules, and are not 

 provided with an investing membrane. A great deal has 

 been said by anatomists concerning this latter point, and 

 many are of the opinion that they are cellular in their struc- 

 ture, being composed of a membrane, with viscid, semi-fluid 

 contents. Without going fully into the discussion of this 

 point, it may be stated that few have assumed actually to 

 demonstrate this membrane; but they have, for the most 

 part, inferred its existence from the fact of the swelling, and 

 as they term it, bursting on the addition of water ; and par- 

 ticularly, as it seems to me, to make the blood-corpuscles 

 obey the theoretical laws of cell-development and nutrition 

 laid down by Schwann. Their great elasticity, the persist- 

 ence with which they preserve their bi-concave form, and 

 their general appearance, would rather favor the idea that 

 they are homogeneous bodies of a definite shape, than that 

 they have a cell-wall with semi-fluid contents ; especially as 

 the existence of a membrane has been interred rather than 

 demonstrated. Their mode of nutrition is like that of any 

 other anatomical elements. They are continually bathed in 

 a nutritive fluid, the plasma, and as fast as their substance 

 becomes worn out and eifete, new material is supplied. In 

 this way they undergo the same changes as other anatomical 

 elements. When destroyed, or removed from the body in 



1 For full directions for the examination of blood stains, the reader is referred 

 to an article on the medico-legal examination of spots of blood by Robin, in the 

 Buffalo Medical Journal, 1857-58. Vol. xiii., p. 555. 



