THE LAWS OF ORGANIC 



and has also to contend against the influence of the 

 cold, whose property it is to constrict the capil- 

 lary vessels, and, by lessening their diameter, to 

 retard the flow of blood to the surface of the body ; 

 but when this condition of atmospheric pressure 

 is conjoined with exercise, the influence of the 

 cold is counteracted. The respiration and circu- 

 lation are much accelerated by exercise, as is uni- 

 versally known, and therefore the blood is trans- 

 mitted in greater quantity, and with superior 

 energy, to every part of the system. It is now 

 external in its distribution, and the effect of the 

 atmospheric pressure is materially augmented by 

 the addition of a new power acting in unison 

 with its own. A greater quantity of blood being 

 determined upon the surface of the body by ex- 

 ercise, and the influence of the diminished pres- 

 sure, the consequence is, that the proportion of 

 this fluid in the lungs is materially lessened ; 

 therefore its stimulating properties and circulation 

 mil be much increased. Many statements are on 

 record which clearly show that the union of the 

 two causes has been attended by epis taxis and 

 hemoptysis, and many other symptoms of san- 

 guineous disturbance ; and the rationale proposed 

 seems to be satisfactory in the solution of the 

 phenomena. The fact that hemoptysis and epis- 

 taxis occur under these circumstances is strongly 

 corroborative of the idea concerning their proxi- 

 mate cause.* 



* Vide Appendix. 



