ON PEARS. 107 



closely exaiiiiiicd, they !iic iVeiiuenily loumJ solLciifd ;uid ol a blackish brown color, and 

 the attachment of the surrounding leaves will begin to be loosened, the whole circulation 

 being cut olF or destroyed. 



If the whole limb is observed, then, in tiiis disease, while it is progressing, a close in- 

 spection reveals patches of a Ijrownish or leaden hue, and a slightly wrinkled slate of the 

 cuticle; the leaves brown in spots, others totally brown and dry, and ready to fall ofl'. If 

 now we make an incision so as merely to raise up the cuticle, tlie cellular tissue below is 

 perfectly brown, or blackish brown; the junction of the bark with the wood is also disco- 

 lored, and the wood beneath soon becomes dry and hard, and perfectly impervious to the 

 fluids of the limb. 



If the above ilesciiptiou is true, our intelligent readers will scarcely fail to recognize in 

 the symptoms and progress of the disease a true vegetable mortification, beginning with a 

 death of the outside, which proceeds from a small surface upwards and downwards, and 

 also inwards. Tiie circulation in the centre of the limb proceeds languidly for some time, 

 so far at least as to furnish nutriment to the extremity, while all below is dead and de- 

 stroyed. So, too, as in mortification of the limbs of animals, a line of separation takes 

 place between the dead and the living parts, beyond which the disease does not extend. 



In accordance, then, with the above remarks, we have in many instances of post mortem 

 examinations, pronounced a verdict oi death from mortification ; at the same time we have 

 been constrained to add that in view of the primary cause we were in the dark. 



There is nothing which conflicts, so far as we know, with the view that all living struc- 

 tures may be subject to death from mortification or gangrene. In animal structures gangrene 

 results from a variety of causes, and is always to be set down as an effect. In aged persons 

 the toes mortify, or the extreme parts which do not seem to be duly supported by the fluids. 

 In cases of high inflammation tl)e j)arts sometimes die or mortify, and are fitially thrown 

 oflf if the part is not a vital out?. It can hardly be supposed, Irowever, that vegetables are 

 liable to attacks of inlhuuniatiun; we may, it is true, suppose that under a hot sun the 

 fluids and the solids may be acted upon in a manner analogous to that which results in 

 inflammation in animals — still we can by no means feel satisfied that is truly the case. 



The gangrene or mortification which occurs in trees, seems often to result from want of 

 vigor or strength in the tissues, thougli by no means are we warranted in drawing the con- 

 clusion that it is always so. When, however, we see a tree with rather delicate leaves, and 

 with long, straggling, pendant branches, losing its leaves and branches in succession, we 

 may suspect that there is a want of ability to supply the amount of sap to preserve the 

 vital principle, and especially where we find that heading in the branches results in stop- 

 ping the progress of the decay, by giving more energy to the remaining parts. 



The death of vegetables from mortification described above, differs materially from death 

 by the girdling of the larvae of insects. In this case there is not that peculiar unhealthy 

 appearance of the tissue of the parts beneath the cuticle, and generally the whole limb 

 dies at once down to the place where the insect has formed its trench. The oak, and in 



