48 



HUMAN BODY. 



corpuscle, but dilute acetic acid dissolves most of them 

 and brings the nucleus into view. These pale corpuscles 

 belong to the group of undifferentiated tissues, and differ in 

 no important recognizable character from the cells which 

 make up the whole very young Human Body, nor indeed 

 from such a unicellular animal as an Amoeba, They have 

 the power of slowly changing their form spontaneously. 

 At one moment (Fig. 12) a pale corpuscle will be seen as 

 a spheroidal mass; a few seconds later processes will be seen 

 radiating from this, and soon after 

 these processes may be retracted and 

 others thrust out; and so the cor- 

 puscle goes on changing its shape. 

 These slow amoeboid movements are 

 greatly promoted by keeping the 

 specimen of blood at the temperature 

 of the Body. By thrusting out a 

 process on one side, then drawing 

 thJ the rest of its body up to it, and 

 its then sending out a process again on 

 the same side, the corpuscle can 

 slowly change its place and creep across the field of the 

 microscope. Inside the blood-vessels these corpuscles exe- 

 cute quite similar movements; and they sometimes bore 

 right through the capillary walls and, getting out into the 

 lymph spaces, creep about among the other tissues. This 

 emigration is especially frequent in inflamed parts, and the 

 pus or "matter" which collects in abscesses is largely made 

 up of white blood corpuscles which have in this way got 

 out of the blood-vessels. The average diameter of the 

 white corpuscles is one third greater than that of the red. 



The Blood Plaques. It has been recently proved that 

 a third kind of corpuscle, the plaque, exists in circulating 

 blood. It is much smaller than the red. When blood 

 is drawn from the vessels, the plaques break up with great 

 rapidity and are destroyed. 



Blood of Other Animals. In all animals with blood the 

 pale corpuscles are pretty much alike, but the red corpus- 

 cles, which with rare exceptions are found only in Verte- 



