336 DIVERSIONS OF A NATURALIST 



a student at Vienna with the great microscopist Strieker. 

 We used the glass-clear connective tissue which forms 

 the " cornea " of the eye, cut from a freshly killed frog. 

 In those days the part taken by these cells in inflamma- 

 tion was being discovered, the name " phagocyte " had 

 not been invented, the part played by them and by 

 bacteria in disease and the suppuration of wounds was 

 unknown, and I had the privilege of introducing Lister's 

 earliest researches on aseptic surgery and on the coagu- 

 lation of the blood to the notice of my friend and 

 teacher. 



This ubiquitous " connective tissue " underlying the 

 skin, pushing its way into and around every part of 

 every structure in the body, is the " source " — the 

 reservoir, as it were — from which the lymph stream and 

 the finest lymphatic vessels take their origin. The 

 question may very naturally be asked, " How is it that 

 the lymph flows along the channels provided by the 

 transparent lymph vessels and is poured through ' the 

 thoracic duct ' into the great vein near the heart ? " 

 If we inject a suitable coloured fluid by means of a 

 needle-pointed syringe into any mass of connective tissue, 

 we can see the fluid pass into the numerous lymph 

 vessels previously invisible, and if we inject into them a 

 weak solution of silver nitrate we can, subsequently by aid 

 of the microscope, make out the structure of the walls of 

 the lymphatics and the lining pavement cells which become 

 stained of a brown colour by the silver when exposed 

 to light. But there is no muscular envelope, nothing 

 like " a lymph-heart " in mammals, to drive the lymph 

 along. There are valves or flexible flaps in the walls of 

 the lymph-vessels, as there are in the veins, and the 

 lymph is driven to the heart by the intermittent pressure 

 upon these valved tubes, caused by the movements of 



