ILLUSTRATIONS (14). ATMOSPHERIC HEIGHT. 295 



arrive at the solution of a great numerical vital problem, since 

 the forms, in accordance with still unexplained laws of uni- 

 versal organism, reciprocally limit each other. But is the 

 number of the organisms a constant number? Do not new 

 vegetable forms spring from the ground after long intervals of 

 time, whilst others become more and more rare, and finally 

 disappear? Geology confirms the latter part of this question 

 by means of the historical memorials of ancient terrestrial 

 life. " In the primitive world," to use the expression of the 

 intellectual Link,* " elements remote from each other blend 

 together in wondrous forms, indicating, as it were, a higher 

 degree of development and articulation in a future period of 

 the world." 



(14) p. 222 "Whether the height of the aerial ocean and its 

 pressure have always been the same." 



The pressure of the atmosphere has a decided influence on 

 the form and life of plants. This life, owing to the fulness 

 and abundance of the leafy organs provided with interstitial 

 openings, is principally directed outwards. Plants mainly live 

 in and through their surfaces, and hence their dependence on the 

 surrounding medium. Animals are more dependant on internal 

 stimuli ; they generate and maintain their own temperature, 

 deriving from muscular movements their electric currents, 

 and the chemical vital processes which arise from and re-act 

 upon those currents. A kind of cutaneous respiration con- 

 stitutes an active vital function of plants, and depends, so 

 far as it is an evaporation, inhalation, and exhalation of 

 fluids, on atmospheric pressure. Hence Alpine plants are 

 more aromatic and hirsute than others, and more amply 

 provided with numerous exhalants.f Zoonomic experiments 

 teach us, as I have shown in another work, that organs are 

 more abundant and more perfectly developed in proportion to 

 the facility with which their functional requirements are 

 fulfilled. The disturbance occasioned in the respiration of 

 their external integuments, by increased barometric pressure, 

 renders it, as I have elsewhere shewn, very difficult for 

 Alpine plants to thrive in the plain. 



* Abhandl. der Akad. der Wise, zu Berlin aus dem J. 1846, s. 322. 

 t See my work, Ueber die gereizte Muskd-und Nervenfaser, bd. ii. 

 B. 142 145*. 



