Circulation of tlie Blood. 139 



less corpuscles occur only exceptionally among the 

 host of red ones. Dr. Carpenter states that for a 

 time they appear identical with the corpuscles found 

 floating in " chyle " and " lymph/' but are liable to 

 change their form ; and that their size is to a remark- 

 able degree similar in all the vertebrated animals, 

 whereas there are great differences in the dimensions 

 of the red corpuscles in the various species. One of 

 the colourless corpuscles may be seen in fig. 5 at the 

 right, and near the top. The " red " corpuscles of 

 the frog are exceedingly thin and flat, except at the 

 centre, where there is an oval or almond-shaped 

 thickening, which can be observed in a few of those 

 in fig. 5. These corpuscles are very pliable, and are 

 to be seen rolling over and over, and bending them- 

 selves at angles ; and occasionally a single one will 

 be observed caught for a few moments by some pro- 

 jection, till other corpuscles in passing sweep it into 

 the current ; and this description will also apply to the 

 movement of the corpuscles in some other animals as 

 observed with the microscope. 



Circulation may be observed in various creatures 

 not belonging to the vertebrated classes ; to which, 

 however, the red corpuscles are peculiar. 



Two objects were always kept in mind namely, to 

 get a sight of the circulation in as many different 

 stages as possible ; and to do it without tyranny or 

 violence. Never yet have I injured fish, frog, or newt 

 on the microscope's stage ; their joyous return to com- 

 parative liberty has gladdened me also, and many a 

 walk I have taken up hill and down dale for the ex- 



