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 011 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 



