NUTRITION. 



747 



smaller fragments, however roughly or strongly 

 the two pieces of glass be made to rub against 

 each other. This is a 'glaring instance' of a 

 compact, tough, elastic, colourless, and fibrous 

 tissue, forming from the colourless elements of 

 the blood ; and the several stages of its formation 

 may be actually seen and determined. Nu- 

 merous corpuscles may be observed, in all these 

 preparations, to have resolved themselves, or to 

 have fallen down into a number of minute 

 molecules, which are spread out over a some- 

 what larger area than that occupied by the 

 entire corpuscles; and although still retaining 

 a more or less perfectly circular outline, yet 

 refracting the light at their edges, in a manner 

 very different from that in which the corpuscles 

 themselves are seen to do. It is from these 

 and various other larger and more irregular 

 masses of molecules on disintegrated corpuscles, 

 that the fibrinous filaments shoot out on all 

 sides, as from so many centres ; or frequently 

 the filaments are more copious in two opposite 

 directions."* 



A different view of the cause of the produc- 

 tion of fibrin, however, has been entertained by 

 some eminent physiologists; and it does not 

 seem right to allow the opinions of Wagner, 

 Henle, and Wharton Jones to pass without 

 notice, even though they appear to the writer 

 to be easily set aside. By these observers, the 

 elaboration of fibrin has been attributed to the 

 red corpuscles, and has been regarded as one, 

 at least, of their special functions. Nearly all 

 the arguments, however, which have led us to 

 assign this duty to the white corpuscles, tell 

 equally against the doctrine now under con- 

 sideration. The presence of fibrin in the circu- 

 lating fluid may be regarded as a universal fact ; 

 but the red corpuscles are restricted to verte- 

 brated animals : how, then, is the plastic element 

 elaborated in the invertebrata ? The number of 

 red corpuscles in the blood of different classes 

 bears an obvious relation to their amount of 

 respiratory power, and to the functional activity 

 of the several organs, which is closely connected 

 with the amount of oxygen introduced into the 

 system ; but it does not bear the same relation 

 with the activity of the formative processes, 

 which may be taking place energetically (as in 

 the developement of the embryo, or in the re- 

 paration of parts in the adult) in a state of 

 functional quiescence. That the proportion of 

 red corpuscles in the blood had a special rela- 

 tion to the nervous and muscular energy of an 

 animal, and to the amount of oxygen consumed 

 by it, has long ranked as a physiological truth ; 

 and the opinion has been gradually gaining 

 ground, that although the liquor sanguinis is 

 undoubtedly affected in a considerable degree 

 by exposure to oxygen in the respiratory capil- 

 laries, the red corpuscles are the special agents 

 by which oxygen is conveyed into the systemic 

 capillaries, that it may furnish the conditions 

 required for muscular contraction and other 

 functional operations, which depend upon a 

 due supply of arterial blood. In the inverte- 



* Transactions of the Provincial Medical Asso- 

 ciation, 1843. 



brated animals in general, the amount of respi- 

 ration is so low, that this special provision is 

 not required. There is an apparent exception, 

 however, in the case of Insects, which have no 

 red corpuscles, and which yet can display a 

 greater amount of animal energy, and which 

 consume (when in a state of activity) a larger 

 quantity of oxygen in proportion to their size, 

 than beings of any other class whatever. But 

 here the exception proves the rule ; for the con- 

 veyance of oxygen through the tissues is not 

 accomplished in Insects by the circulating fluid, 

 which has a comparatively sluggish movement, 

 but is effected more directly by the ramifying 

 tracheae, which introduce air into the minutest 

 portions of the structure. 



The pathological evidence that the red cor- 

 puscles are not the elaborators of the fibrin, 

 appears to the writer to be quite conclusive. 

 Whilst the quantity of fibrin is so remarkably 

 increased in inflammation, the number of red 

 corpuscles undergoes no decided change. 

 Again, the augmentation of the fibrin is not in- 

 compatible with a chlorotic state of the blood ; 

 the peculiar characteristic of which is a great 

 diminution in the proportion of red corpuscles. 

 By such alterations, the normal proportion be- 

 tween the fibrin and the red corpuscles, which 

 may be stated as A : B, may be so much altered, 

 as to become, in inflammation, 3\ : B, in chlo- 

 rosis A : 5 B. Again, in fever, the characteristic 

 alteration in the condition of the blood appears 

 to be an increase in the amount of red cor- 

 puscles, with a diminution in the quantity of 

 fibrin ; yet if a local inflammation should 

 establish itself during the course of a fever, the 

 proportion of fibrin will rise ; and this without 

 any change in the amount of corpuscles. 

 Lastly, the effect of loss of blood has been 

 shown by Andral's investigations to be a marked 

 diminution in the number of red corpuscles, 

 with no decided reduction in the quantity of 

 fibrin, even when this is much above its normal 

 standard ; and in this condition of the blood it 

 has been observed by Remak that the colourless 

 corpuscles are very numerous. 



Formation of tissue. With the elaboration 

 of the alimentary materials into fibrin, the pre- 

 paratory processes of nutrition may be regarded 

 as terminating ; since the next step is the trans- 

 formation of this substance into organised tissue. 

 Upon the mode in which this is effected, much 

 light has been thrown by recent enquiries ; but 

 several points still remain obscure. We shall 

 endeavour, in the following account, to dis- 

 tinguish what has been satisfactorily ascertained 

 from what is merely hypothetical. 



That the particles of perfectly-elaborated 

 fibrin are capable, in solidifying, of spontaneously 

 assuming a definite arrangement, cannot now 

 be questioned. In the ordinary crassamentum 

 of healthy blood, this arrangement can be seen, 

 by examining thin slices under the microscope ; 

 especially after the clot has been hardened by 

 boiling. A number of fibres, more or less dis- 

 tinct, may be seen to cross one another ; form- 

 ing by their interlacement a tolerably regular 

 network, in the meshes of which the red cor- 

 puscles are entangled. This fact was known to 



