88 LECTURE m. 



lity of the capillaries really had reference to small arte- 

 ries and veins, the calibre of which grows narrower 

 through the contraction of their muscular coats, or wider 

 upon the occurrence of relaxation in consequence of the 

 pressure of the blood. This is one of the first facts, and 

 an important one it is, which have resulted from the 

 more accurate histological knowledge of the smaller and 

 larger vessels, and it shows us that we cannot speak of 

 the general properties of vessels, inasmuch as the capil- 

 laries differ essentially in structure from the small arte- 

 ries and veins. These are composite structures, partak- 

 ing of the nature of organs, whilst a capillary vessel is 

 rather a simple histological element. 



Now that we have, gentlemen, completed a very 

 general survey of the physiological tissues, the question 

 arises, how the pathological ones in their turn comport 

 themselves. By pathological tissues, of course, those 

 only can be meant which really constitute pathological 

 new formations, and not physiological parts which have 

 simply undergone alteration in consequence of some 

 deviation from the normal processes of nutrition. We 

 have in them to deal with genuine neoplasms, with the 

 additional matter furnished by the growth of new tissues 

 in the course of pathological processes, and the question 

 is, whether the general types which we have established 

 for the physiological tissues will also be found to hold 

 good in the case of the pathological ones. To this I un- 

 reservedly reply, yes ; and however much I herein differ 

 from many of my giving contemporaries, however posi- 

 tively the peculiar (specific) nature of many pathological 

 tissues has been insisted upon during the last few years, 

 I will nevertheless endeavour in the course of these lec- 

 tures to furnish you with proofs that every pathological 

 structure has a physiological prototype, and that no 

 form of morbid growth arises which camiot in its ele- 



