LYMPHATIC SYSTEM. 177 



has been considered as so strong in favour of absorption by the 

 common veins, is liable to objections. And lastly, a seventh 

 argument used in favour of common veins absorbing, was, that 

 many animals were destitute of any other vessels which could 

 do that office. This was supposed to be the case with birds, 

 fish, and amphibious animals; all of which some anatomists 

 did not hesitate to affirm must want every part of the lymphatic 

 system, and with great appearance of reason; since in the 

 smallest quadruped they could easily find either lacteals or 

 lymphatic glands upon the mesentery, but in the- largest bird 

 or fish neither lacteal vessel nor conglobate gland could be 

 seen. And if these animals (said they) be without the lym- 

 phatic system, absorption in them must be performed by other 

 vessels, viz. the common veins ; and if in them the common 

 veins can do the office of absorption, why should not they 

 likewise perform it in the human body, where such veins equally 

 exist. 1 But this argument is overthrown by the lymphatic 

 system being now discovered in all these animals. 



Such are the arguments produced in favour of the common 

 veins doing the office of absorption, a doctrine which has lately 

 been espoused by that excellent anatomist, Dr. Meckel, to 

 whose observations, though agreeing with some already men- 

 tioned, it may be necessary to pay a particular attention. 



Dr. MeckeFs conclusions in favour of this doctrine are 

 made entirely from injections in dead bodies. For, having 

 filled the common veins by injecting mercury into the lympha- 

 tic glands, into the excretorj- ducts of the breasts, into the 

 vesicula seminalis, into the hepatic ducts, and into the urinary 

 bladder, he concludes that the veins open into these parts in 

 the living body to absorb from them. 2 A conclusion which 

 is already proved to be liable to considerable objections, as 

 we never can be sure whether our injection, in getting from 

 these cavities into such veins, had gone by a natural or by a 

 forced passage. Dr. Meckel does indeed mention that there 

 were no marks of an extravasation in his experiments. Per- 

 haps it might have been too small for observation. Nay, we 

 have even reason to believe that as the small vessels of the 



1 See Prof. Monro's Obs. Anat. Phys. p. 57 ; Dr. Haller's Elena. Phys. lib. xxiv, 

 sect. 2, 3, pp. 66-7. 



2 See his Nova Experimenta et Observations, Berol. 1772. 



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