156 LYMPHATIC SYSTEM. 



and likewise in having the vessel, which goes from the net- 

 work into the vein small in proportion to the size of that net- 

 work ; so that the lymph must be lodged some time in those 

 parts before it is poured into the mass of blood. In birds I 

 also observed something like this, their lymphatic system being 

 enlarged, or varicose at different parts ; but these enlargements 

 are small in proportion to those above mentioned in fish and 

 in the turtle. 



As to the manner of discovering those vessels in a fish, one 

 might naturally suppose, that when it is known where the re- 

 ceptaculum, or any of the larger parts of this system lie, it 

 could not be difficult to find them ; but the coats of these ves- 

 sels are so thin and transparent, that it is by no means easy. 

 The readiest way of finding the whole system is, to look for 

 one of the vessels which lie close to the skin ; as, for instance, 

 that which runs up exactly on the middle of the belly of the 

 haddock, cod, and other fish of the same shape. This vessel is 

 easily seen, as it grows pretty large at its upper part, near the 

 head, and if a pipe be introduced, the whole system may be 

 filled by its means. 



It is partly owing to the ease with which those vessels 

 may be seen, after discovering where their larger branches lie, 

 that I have not added a figure of this system in a fish. Indeed 

 it would be almost impossible to express all its parts in one 

 figure, from the numerous and intricate communications of 

 those vessels near their termination in the common veins. 

 But I formerly laid before the Royal Society a haddock with 

 its lymphatics and blood-vessels filled with coloured injections, 

 to be compared with the description which was printed in the 

 Philosophical Transactions, vol. 59. And those that are de- 

 sirous of prosecuting this subject further, will, I flatter myself, 

 find it an easy matter to fill the whole system by attending to 

 what I have said above. 



