SUMMARY AND CONCLUSIONS 



In concluding this part of the record of observations on the on- 

 togeny of certain axial systemic lymphatic channels in embryos 

 of the domestic cat, I desire very briefly to contrast the results of 

 this investigation with the tenets of the theories of mammalian 

 lymphatic development divergent from the views here expressed. 

 This is not done for the purpose of inciting or prolonging a con- 

 troversial discussion. As far as I am personally concerned, con- 

 troversy is at an end, because I believe that I have furnished posi- 

 tive evidence of the correctness of the opinion which I have 

 maintained during the past six years, from the tune on when my 

 investigations first warranted definite conclusions. The results 

 given in previous publications, and more in detail in the preceding 

 pages, afford to me a sound basis for interpreting my findings of 

 adult as well as of embryonic organization of the lymphatic system 

 both in mammals and in the other vertebrate classes. Conse- 

 quently, until these results are successfully accounted for on an 

 equally broad and phylogenetically consistent hypothesis differ- 

 ing from my own interpretation, and until the deductions based 

 on them are shown to be erroneous by equally full and compre- 

 hensive proofs, I shall rest quite satisfied with the position I have 

 reached on this question. 



It may, however, serve a useful purpose in enabling scientific 

 men in general to draw their own conclusions, if the facts here 

 offered are contrasted in a final review with the divergent theories 

 of lymphatic development which have been propounded in the 

 last decade. 



In regard to the view which supposes the mammalian lymphatic 

 system to arise by an outgrowth or bud from one or more sacs of 

 venous origin and thence to extend by a continuous centrifugal 

 process from centre to periphery, terminating in closed lymphatic 

 capillaries, I find little to say. 



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