428 



OF NUTRITION. 



Fig. 100. 



Corpuscles of Human Blood, magnified about 500 

 diameters; A, single red particles; 1, 1, their flattened 

 face; 2, a particle seen edgeways, three-quarter view; 

 B, aggregation of particles in a columnar form; c, co- 

 lourless corpuscles. (After Wagner.) 



Fig. 101. 



cles of Mammalia, there has been 

 considerable difference of opinion 

 amongst microscopists ; some main- 

 taining that it can be brought into 

 view by treating them with acetic 

 acid, whilst others deny that any de- 

 finite appearance is thus produced. 

 The researches of Mr. Gulliver and 

 Mr. Wharton, however, appear to 

 the Author quite conclusive as to 

 the non-existence, in the red parti- 

 cles of Mammalia (even in the oval 

 discs of the Camelidas), of any thing 

 at all analogous to the nucleus, 

 which is to be seen in the blood- 

 discs of Oviparous Vertebrata. The 

 corpuscles, when emptied of their coloured contents by the action o'f water, 

 exhibit no trace of it in Mammalia ; though the same process brings them 

 clearly into view in the oval blood-discs of all other Vertebrata. The central 

 matter in the Mammiferous blood-disc, which undergoes coagulation under the 

 influence of acetic acid, is therefore not to be regarded as a true cell-nucleus, 

 which is evidently the character of the central spot on other blood-discs ; but 

 is rather a collection of albuminous particles, which are coagulated by the 

 action of the acid upon them, just as they would be in the liquor sanguinis or 

 in the serum of the blood. 



571 . In all Oviparous Vertebrata, 

 without any known exception, the 

 red corpuscles are oval, the propor- 

 tion between their long and short 

 diameters, however, being much 

 subject to variation ; and their nu- 

 clei may always be brought into 

 view by treatment with acetic acid, 

 when not at first visible. In the 

 red particles of the Frog, which are 

 far larger than those of Man, a nu- 

 cleus can be observed to project 

 somewhat from the central portion 

 of the oval, even during their circu- 

 lation, and it is rendered extremely 

 distinct by the action of acetic acid ; 

 this dissolves away the remainder of the particle and gives an increased 

 opacity to the nucleus, which is then seen to consist of a granular substance. 

 In the still larger blood-disc of the Proteus and Siren, this appearance is yet 

 more distinct ; the structure of the nucleus being so evident, without the addi- 

 tion of acetic acid, that its granules can be counted.* 



or to ascertain their true forms; as the serum of one Mammal reacts injuriously on the 

 blood of another. See Philos. Magaz., Jan. and Feb., 1840. 



* As Professor Owen's interesting account of the blood-discs of the Siren may not be 

 generally accessible (Penny Cyclopedia, Art. Siren'), the leading facts in it will be here 

 stated. This animal agrees with the Proteus and other species in being perenni branchi- 

 ate (43); and, as in all its congeners yet examined, the blood-discs are of very large 

 dimensions. They are usually of an oval form, the long diameter being nearly twice the 

 short; and the nucleus projects slightly from each of the flattened surfaces. Considera- 

 ble variety in the form of the disc presented itself, some of the corpuscles being much 

 less oval than others; but the nucleus did not partake of these variations in nearly the 



Particles of Frogs Blood; 1. 1. their flattened face; 

 2, particle turned nearly edgeways ; 3, lymph-globule ; 

 4, blood-corpuscles, altered by dilute acetic acid. Mag- 

 nified 500 diameter. (After Wagner.) 



