Blood and Blood Vessels. 221 



the blood-stream finally, that it is in some way derived 

 from the blood, etc. But there is no clear perception of 

 these relations, and it is impossible that there should be 

 with the teachings that are prevalent. 



The books represent the lymph as passing through the 

 capillaries; but, if any explanation of this process is given 

 at all, it is represented as a filtration — very much of the 

 character of that " filtration " of urine through the capil- 

 laries of the Malpighian capsules, which has been so com- 

 monly taught up to the present as dependent almost solely 

 on blood pressure. 



This doctrine has seemed to me so utterly at variance 

 with all sound biological laws, that for three or four years 

 I have been accustomed to teach in my lectures, and have 

 recently published in my text-book, a theory which I must 

 present to you with brevity, but which I am sure you will 

 see places the physiologist, the pathologist, and the prac- 

 titioner of medicine on an eminence from which they can 

 view the events of the body in an entirely new light. It is 

 simply this : The capillaries of the body are glands. They 

 are glands not only in the glomeruli of the kidney, but 

 everywhere else. So far as I know, I have been the first 

 to teach this doctrine ; I must therefore give you, at least 

 in a general way, the reasons for my conviction. 



In the first place, I should be prejudiced against any bio- 

 logical doctrine that would represent a living structure as 

 acting as a mere filter, or as teaching that osmosis played 

 any considerable part or, in the strict sense, any part at all 

 when living structures, " membranes " or other, were con- 

 cerned. There seem to be no facts that can not be better 

 explained without such an assumption ; and, even if this 

 were not the case, it is better not to construct a theory at 

 all, but simply confess ignorance and wait, than one which 

 like this is radically opposed to all sound conceptions of 

 living structure. 



To believe that the lymph which bathes the various tis- 

 sues is everywhere identical in composition, is to overlook 

 the relations of the blood and blood-vessels lo the tissues 



