THE BLOOD CORPUSCLES. 59 



Many microscopic observers doubt or deny the existence of a cell- 

 coat or envelope, not only in the human and general mammalian 

 blood-corpuscle, but even in the larger corpuscles of the frog. They 

 describe these bodies as little soft, elastic, homogeneous masses, having 

 the outer layer a little more condensed than the interior, excepting the 

 so-called nucleus when it is present. By some, the non-nucleated 

 mammalian red corpuscles are regarded as free nuclei, specially modi- 

 fied (Gulliver, W. Jones); but it is said that they even possess a double 

 cell-wall (Roberts); so that they might be regarded as small cells, com- 

 pletely filled by a vesicular nucleus* 



The white corpuscles of the blood, much fewer in number than the 

 red, the proportions between them averaging from 2 to 3 in 1000, are 

 colorless, transparent and spherical nucleated cells, having no distinct 

 envelope, but a finely granulated surface, granular contents, and, as 

 shown by the action of acetic acid, a simple or compound nucleus in 

 their interior, Fig. 38, a. They are not so heavy as the red corpus- 

 cles, and refract light more strongly. They do not run together into 

 rolls like coins, nor do they change their form by bending within the 

 vessels. Lastly, they are more uniform in size and shape in different 

 animals than the red corpuscles, being nearly of the same size and 

 character throughout, however widely the colored ones differ in these 

 respects. They have a general resemblance to the corpuscles of the 

 lymph, to be immediately described ; but these latter are said, as we 

 shall see, to be nuclei and not nucleated cells. After a meal, true 

 lymph-cells also may be sometimes found in the blood. 



White corpuscles in animals. In the frog, the proportion of the white cor- 

 puscles to the red is 1 to 16 in winter, and 1 to 6 in summer. The singular 

 little fish named the lancelet, or amphioxus, is the only one of the so-called 

 vertebrate animals (of which it is the simplest yet discovered) in which the 

 blood has no red corpuscles, but only colorless ones. The corpuscles found in 

 the blood of still lower animals, such as cuttle-fish, insects, crabs, and others, 

 are also generally free from color, and are usually discoid in shape. 



When blood is diluted with water, the red corpuscles swell, become 

 indistinct, and finally burst : when any agent, such as salt or syrup, 

 which increases the density of the blood, is added to it, these same 

 corpuscles shrink and assume various irregular forms. Sometimes, 

 whilst being examined under the microscope, without any known 

 cause, they become indented or jagged at the edges, or otherwise 

 altered in shape. In certain cases this may be owing either to pres- 

 sure, evaporation, special aggregation, or decomposition. The white 

 corpuscles, on the other hand, have been seen to thrust out little buds, 

 and so even become stellate, whilst they may yet be regarded as living. 

 'It has been said that oxygen gas distends the red corpuscles, whilst 

 carbonic acid gas shrinks them up ; but this is not well established. 

 Acetic and other acids swell and ultimately dissolve them. The ap- 

 pearance of an envelope, and the pale nucleus or nuclei of the white 

 corpuscles, are best seen after the action of very dilute acetic acid, 

 when the corpuscle presents a smooth outline, and the nucleus often a 

 reddish hue : very strong acetic acid causes the nucleus to divide into 

 two or three separate parts. 



