INVOLUTION 485 



fraught with great potentialities for the furtherance of 

 nature's plans and the accomplishment of nature's work. 



Consistence and depth of skin and completeness of 

 underpacking being chiefly responsible for the regulation 

 of the incidence of surface ageing, it follows that that 

 incidence must be determined by the changing proportions 

 of these elements to each other, and by the altering pro- 

 portion in anatomical space they occupy with relation to 

 the deeper-seated structures during the various stages of 

 the process. 



The skin being mainly made up of two vascular 

 elements, whose circulatory vascular phenomena are entirely 

 different the one from the other, it behoves us to analyse 

 to some extent the character of these phenomena, in order 

 to arrive at more exact and definite ideas than we have 

 hitherto held with regard to the rationale of external 

 ageing. 



Leaving out, still, the lymphatic circulation of the 

 structures involved, as not decidedly necessary in the fol- 

 lowing analysis, we would premise that there are two circu- 

 lations involved in particular in the process of external 

 ageing, one haemal and the other neural. The first, or 

 haemal, is a circulation through an arterial vasculature 

 ending in a capillary network of intermediate minutely 

 divided and anastomosing vessels, where the phenomena of 

 haemal change from arterial into venous takes place, and 

 where the venous vasculature re-collects, for renewed 

 arterialisation, the minutely broken up capillary currents. 

 In this circulation there is no excretion of the haemal 

 elements into the cuticular textures through which they 

 pass save those of metabolism, and, consequently, no macro- 

 scopic deposit in the matrix of the skin, and no material 

 shedding, which on " setting " can add to its thickening 

 and consistence^ or depth, the circulation being into and 

 out of the anatomical elements of the skin, with the secured 

 freedom and hydraulic strength and completeness of .an 

 uninterrupted current, perfected by ubiquitous capillary 

 vascular anastomoses and open capillary channels. This 

 circulation, the haemal, we must, therefore, eliminate from 

 the " possible " agents in the process of ageing, at any rate 

 in so far as it can be held responsible for the increasing 



