BY DR. KLEIN. 19 



movement. Three forms may be distinguished, which we 

 will examine in succession : 



1. Common Large Colorless Corpuscles. Supposing 

 that a few moments have elapsed since the preparation was 

 made, some of these pale corpuscles are sure to be seen float- 

 ing hither and thither in the liquid with a rolling movement. 

 The}' are much more numerous than the other forms. 



Fix the attention on one of these bodies, and observe, first, 

 that it is so transparent that, as it rolls over and over, a single 

 granule embedded in its substance may be kept constantly in 

 view. Continuing the observation, notice that the surface of 

 the corpuscle, at first smooth, gradually becomes uneven. 

 The cause of the unevenness is this. The surface is beset 

 with a greater or less .number of filamentous appendages, 

 varying in length, and distributed over the surface with 

 variable uniformity. These seem to consist of the same 

 material as the body of the corpuscle. When they are short 

 the}' may be compared to prickles, when longer they are often 

 bent at the point. Sometimes we see one of the processes 

 lengthen itself, while another disappears; sometimes a whole 

 group of processes push out on one side, while others are re- 

 tracted on the opposite side. Occasion all} r , from the small- 

 ness and great number of the processes, it is scarcely possible 

 to be sure as to the changes which occur. Here is a corpuscle 

 which appears to be gradually enlarging. Let us follow the 

 changes it will undergo. Already it covers a space three or 

 four times as great as before. Simultaneously with this in- 

 crease of size, its form becomes irregular, and (as may be 

 ascertained by the fine-adjustment screw) its vertical measure- 

 ment is diminished, so that it now constitutes a thin layer 

 limited by a distinct contour. Soon, however, the circumfer- 

 ence thins out in certain directions, so that the edge can no 

 longer be discerned ; the only evidence of its existence in these 

 attenuated parts being that the field appears to be covered 

 with a granulous film. 



In the layer of protoplasm we have now before us, some 

 parts are hyaline, or contain at most a few minute granules. 

 In others, you will notice, there are clear spots with well-de- 

 fined contours, which differ indefinitely in size, and have no 

 definite arrangement. Many of them are so clear that they 

 look like perforations. It is characteristic of them that they 

 are undergoing change, both as regards their relative position 

 and relative distinctness, some coming into view while others 

 are fading. These we call vj^y^s. They are believed to be 

 cavities filled with liquid, the origin of which is due to the 

 constant commotion of the protoplasmic mass. If this be so, 

 it is easy to understand why it is that they appear and dis- 

 appear so rapidly. We next observe that at some part of the 



