MICROSCOPY. 373 



to be chemically united with the protoplasm, and it escapes 

 readily, even by the action of very weak reagents. The nu- 

 cleus represents an oval vesicle containing most probably a 

 more or less dense liquid, with a number of larger and small- 

 er granules. These lirst expand and then dissolve in water, 

 increasing the volume of the whole contents and expanding 

 the walls of the nucleus. The colored corpuscles of the frog- 

 resemble in form, as also in chemical and physical properties, 

 those of the Amphiuma yhut are less than half their size; when 

 they are treated with water the coloring matter gradually dis- 

 appears, but their outline is still visible, appearing in the form 

 of a delicate double contour, which is the membranous layer 

 of the corpuscle. The examination of the colored blood-cor- 

 puscles of man and the other mammalia is more difficult, in 

 consequence of their smaller size. Those of man represent 

 minute bi-concave disks with rounded margins, and a diam- 

 eter of about -j-jjo- mm. In a state of rest the outline is perfectly 

 round ; but when this outline is most distinctly in focus, the 

 centre to about the extent of one third the whole diameter 

 appears light. Between this and the bright margin is a vary- 

 ing shade caused by the form of the corpuscle. No trace of 

 a membrane or a membranous layer can be discovered in 

 the fresh blood-corpuscle of man. In the paper is a full dis- 

 cussion of the various changes in form and appearance of the 

 blood-corpuscles due to external causes, and especially in 

 connection with varying temperatures; also to the manifes- 

 tation of spontaneous motion, due, as is stated, to living pro- 

 toplasm, so that they have an inherent power of contracting 

 and a^ain resuming their original form. The changes in 

 form, which increase rapidly in proportion to the length of 

 time after removal from the living: tissue seem to be the re- 

 suit of the last vital actions of the blood-corpuscle, and por- 

 tend its death. Dr. Schmidt concludes that the function of 

 the colored blood-corpuscles is at least partly secretory ; he 

 considers them as true glandular cells, engaged in appro- 

 priating certain materials from the plasm of the blood, in 

 order to transform them into other bodies by virtue of 

 their secretory power, and finally to return them to that 

 fluid, in the condition required for the subservience of oth- 

 er purposes, such as the preservation of the normal con- 

 stitution of the blood, as well as the nutrition of the vari- 



