326 REPAIR OF LOSSES OF SUBSTANCE. 
place of such as are lost during the earlier periods of develop- 
ment. 
391. When an entirely new structure is to be formed,—as 
for the closure of a wound, the union of a broken bone, or the 
repair of any other injury,—the process is of a kind very much 
resembling the first development of the entire fabric. The 
neighbouring vessels pour out their liquor sanguinis, which is 
known to the Surgeon under the name of coagulable lymph ; 
this fills up the open space, and forms a connecting medium 
between the separated parts. If this intervening layer be 
thin, the two sides of the wound may adhere so closely as to 
grow together without any perceptible interposition of new 
substance ; this is what is called “healing by the first inten- 
tion.” But if the loss of substance has been too great to 
allow of such adhesion, the vacant space is filled by the 
gradual organization of the coagulable lymph; and this may 
take place in one of two very different modes, the determina- 
tion being chiefly dependent on the condition of the wound 
as to seclusion from air or exposure to it. 
392. The former of these conditions is by far the more 
favourable of the two ; for the reparative material is usually 
developed gradually but surely into fibrous tissue, without 
any loss, and with very little irritation either in the part 
itself or in the system at large. This process seems to take 
place naturally in cold-blooded animals, even in open wounds; 
the contact of air not having that disturbing influence in 
them, which it exerts in warm-blooded animals. And Nature 
frequently endeavours to bring it about in the superficial 
wounds of warm-blooded animals, by the formation of a large 
scab, which protects the exposed surface ; but this happens 
much less frequently in the Human subject than it does 
among the lower animals, the unnatural conditions in which 
a large proportion of the so-called civilised races habitually 
live (especially deficient purity of the air, continual excess in 
diet, and the frequent abuse of stimulants) being unfavourable 
to it. The performance of many operations which formerly 
left open wounds, in such a manner that the air may be 
effectually excluded by a valvular fold of skin, is one of the 
greatest improvements in modern Surgery. 
393. In an open wound, on the other hand, which is 
healing by the process termed “ granulation,” the reparative 
