BLOOD. 



409 



pearance or disposition of the globules in 

 question, when it occurs, seems to me to 

 depend on an alteration of these corpuscles. 

 In examining the blood of frogs diluted with 

 thin syrup, the globules occasionally appeared 

 to me to become turgid, but not to be 

 distended equally in every part; the exterior 

 vesicle then remained attached to the centre of 

 the internal nucleus, whilst it became puffed 

 all around. I have seen a globule thus altered 

 in its form, presenting three very distinct en- 

 largements in the course of its long diameter, 

 the two lateral of which exceeded the median 

 one in extent. I should therefore be led to 

 imagine that by the effect of an endosmosis 

 these vesicles may occasionally absorb the 

 water of the serum, and that this fluid, accu- 

 mulating around the central nucleus, without, 

 however, separating this corpuscle from its 

 envelope, gives to the globule in general the 

 form of a biconcave disc, as described by Dr. 

 Young. This appearance, which is very com- 

 mon in the human blood, agrees extremely 

 well with the description of Dr. Hodgkin and 

 Mr. Lister, but we do not imagine that this is the 

 normal condition, and we are persuaded that 

 if these very scrupulous observers would but 

 extend their inquiries to the blood of those 

 animals in which the globules are most easily 

 studied, they would return to and espouse 

 the opinions of Hewson and of Prevost and 

 Dumas in regard to the particular point at 

 issue. 



In the normal state, the membranous vesicle 

 of the globules of the blood appears perfectly 

 smooth among vertebrate animals ; but among the 

 invertebrata its surface is uneven and nodulated 

 like that of a raspberry, as we have already 

 said. Hewson, however, observed that when 

 the blood of the vertebrata began to putrefy, 

 the globules then presented an appearance 

 analogous to what we have remarked in those of 

 the Crustacea and mollusca. In the mammalia 

 the central nucleus is circular and depressed, 

 and in all this class of animals it appears to be 

 similar in size. In the oviparous vertebrata, it 

 is on the contrary elliptical in figure, though, 

 according to Messrs. Prevost and Dumas, it 

 acquires this figure in consequence of a par- 

 ticular substance being fixed around it, itself 

 being in reality circular, as among the mam- 

 malia. 



It frequently happens that other smaller 

 corpuscles than the globules of which we have 

 treated hitherto are observed swimming in the 

 serum. These are of a whitish colour and simi- 

 lar to the molecules that occur in almost all 

 the fluids of the animal economy. The resem- 

 blance that exists between these corpuscles and 

 the central nuclei of the proper globules of 

 the blood might lead to the belief that they 

 were nothing more than the central nuclei 

 divested of their coloured envelope ; but in 

 several of the inferior tribes, as the river-crab 

 and certain mollusca, in the blood of which 

 they occur in very considerable numbers, the 

 central nuclei of the globules are much larger, 

 and it is impossible to confound the two toge- 



ther. These then are to be regarded, not as 

 globules of the blood, properly so called, 

 altered in any way, but as globules of albumen 

 or fibrine. These substances, in fact, have 

 always the appearance of being made up of 

 circular corpuscles of extreme minuteness when 

 by any means they are brought into the solid 

 state ; and we are led to believe that even 

 when dissolved or suspended in water they 

 still preserve this peculiar disposition, and only 

 escape detection under the microscope by their 

 dissemination and transparency. 

 To recapitulate, then, we find : 

 1st. That the globules of the blood are mem- 

 branous sacs inclosing a solid flattened nu- 

 cleus in the form of a disc, in their interior. 



2d. That their form and their dimensions 

 vary among animals of different species, but 

 that in the same animal they all bear the 

 strongest resemblance to one another. 



3d. That in the mammalia these corpuscles 

 are circular and smaller than in any other class 

 of animals. 



4th. That in birds the globules of the blood 

 are elliptical and larger than in the mammalia ; 

 their dimensions vary slightly in different 

 genera, but this variety does not seem to ex- 

 tend further than to the admeasurements of 

 their long diameters. 



5th. That in vertebrate animals with cold 

 blood the globules are also elliptical, but that 

 their dimensions are much greater and vary 

 more extensively in different classes ; reptiles, 

 more especially the batrachia, are of all animals 

 those in which the globules of the blood are 

 the largest. 



6th. That in the invertebrata the globules of 

 the blood are more or less regularly circular in 

 shape, and are also of very considerable dimen- 

 sions. 



It appears to be especially owing to the 

 presence of the globules, the common physical 

 properties of which we have thus far studied, 

 that the blood owes its power of arousing and 

 keeping up vital motion in the animal economy. 

 We observe, in fact, that if an animal be bled 

 till it falls into a state of syncope, and the 

 further loss of blood is not prevented, all 

 muscular motion quickly ceases, respiration is 

 suspended, the heart pauses from its action, 

 life is no longer manifested by any outward 

 sign, and death soon becomes inevitable ; but 

 if, in this state, the blood of another animal 

 of the same species be injected into the veins 

 of the one to all appearance dead, we see with 

 amazement this inanimate body return to life, 

 gaining accessions of vitality with each new 

 quantity of blood that is introduced, by-and- 

 bye beginning to breathe freely, moving with 

 ease, and finally walking as it was wont to do, 

 and recovering completely. This operation, 

 which is known under the name of transfusion, 

 proves better than all that can be said the 

 importance of the action of the globules of the 

 blood upon the living tissues; for if, instead of 

 blood, serum only, deprived of globules, be 

 employed in the same manner, no other or 

 further effect is produced than follows the in- 



