ABSORPTION. 1G1 



Drs. Camus and Gley found in the sympathetic, below the first 

 thoracic ganglion, nerves which contract and dilate the thoracic duct; 

 usually the effect is one of dilatation. 



Formation of Lymph. 



About 1847 Ludwig and DuBois Reymond began to explain the 

 phenomena of life by the law of physics and chemistry. Since the 

 middle of the eighties of the last century, owing to the failure to 

 explain several phenomena, there has arisen a school of Neovitalists, 

 who explain the same observations as being due to vital activity. 

 The secretion of lymph is one of these cases in point. 



There are three theories which explain the secretion of lymph : 



1. Ludwig's or the Filtration Theory, which requires that the 



pressure be higher on one side of the membrane than on the other. 



Fig. 46. Dog with Medulla Divided. (L. CAMUS and E. GLEY.) 



Ex, Irritation of the lower end of the thoracic sympathetic below the stel- 

 late ganglion. C.th, Drops of lymph from the thoracic duct, indicated by the 

 vertical lines. The experimenters were very careful that during the irritation 

 of nerve neither the carotid nor 'the jugular pressure was altered. Dilatation 

 of the thoracic duct by irritation of the thoracic sympathetic, causing an 

 acceleration of the flow of lymph. 



The blood-pressure in the capillaries is greater than the pressure 

 outside the capillaries in the lymph-spaces. Hence, the diluted 

 plasma or lymph will filter through the capillaries. 



By this exudation the interstitial pressure always tends to the 

 same height as the intracapillary pressure the stronger the intra- 

 capillary pressure, the stronger the interstitial pressure. On the 

 other hand, the stronger the interstitial pressure, the more easily 

 the lymph will be absorbed by the lymphatic capillaries. We must 

 admit, with Ludwig's filtration theory, that the pressure of the blood 

 is a powerful cause in the circulation of the lymph, and this can 

 be easily shown by section and irritation of the spinal cord, after a 

 cannula has been introduced into the thoracic duct, where the lymph- 

 flow decreases with the dilatation of blood-vessels on section of the 



cord and increases on irritation of the cut section. 



11 



