514 BIOLOGICAL PHYSICS 



order that the lymphatic vasculature should have to deal 

 alone with the effete lymph resulting from tissue waste. 

 We are warranted in assuming, therefore, that this is 

 effected by the same cell and fibre distributive and 

 circulative machinery, as that by which the corpuscular 

 metabolic elements are circulated and distributed. The 

 existence of such restricted and safeguarded blood-circula- 

 tory provisions obviate the occurrence of admixture of 

 physiologically pure haemal lymph, with effete and nox- 

 ious tissue lymph, and secures the performance of the 

 process of nutrition in an unincumbered and aseptic 

 manner. 



Furthermore, in the economy of aeration or oxygenation 

 of the blood, we have become convinced that we have a 

 great supplementary respiratory mechanism in the system ot 

 pneumatic spaces occupying the face and base of the skull, 

 a series of spaces which, besides that of respiratory supple- 

 mentation, no doubt perform most important mechanical 

 and other offices. These spaces are generally symmetrical 

 in topographical arrangement, and conform to a uniform 

 general plan of anatomical disposition, but, in individual 

 cases, depart considerably in both respects from these 

 conditions ; they are lined by a very thin mucous mem- 

 brane, which, therefore, easily lends itself to the occurrence 

 of osmosis and chemical interchange between the air 

 occupying them and the blood circulating in their walls, 

 by diffusion and consequent synthetic and analytic re- 

 arrangement of the elements occupying the respective 

 areas. In such, what we would call conspicuous, 

 seemingly purposive, arrangements, who can fail to 

 recognise that we have here an adaptation of the prin- 

 ciple of respiratory function to the local wants of the 

 principal vital organs and structures of the body? and, 

 therefore, that we are warranted in claiming their special 

 local anatomical dispositions and arrangements as supple- 

 mentary or cephalic lungs^ and that they must perform 

 functions proportionately important in the great function 

 of blood purification in connection with central nervine 

 function, cerebral and peripheral ? Moreover, the close- 

 ness of the anatomical relationship between these cephalic 

 lungs and the overlying brain structures, lends support 



