418 Notes. 



6.40 p.m. (fig. 28) three leucocytes were seen apart, each contain- 

 ing pigment. The original phagocyte now contained several 

 vacuoles and some pigment, and was very sluggish. 



Some time later the cover-slip was separated from the slide 

 and stained by Leishman's method, and examined under objec- 

 tive -^ in. Several polymorphonuclear leucocytes were found 

 (fig. 29), each containing pigment granules in a large vacuole, the 

 cytoplasm also being vacuolated and staining feebly : changes no 

 doubt due to the slow death of the leucocyte. 



Evidently, then, these polymorphonuclear leucocytes were the 

 phagocytes concerned, and the full process was (1) ingestion and 

 destruction of a crescent, (2) attempted destruction of the re- 

 maining pigment, introducing (3) a union of several leucocytes, 

 apparently to reinforce the first one, and (4) the removal of some 

 of the pigment by these new comers. 



Whether the crescent was still alive at the moment of ingestion 

 is uncertain. It is also difficult to say how far the process de- 

 pended on the conditions of observation, and as to whether it occurs 

 intra vitam in the circulating blood. 



Similar observations were made on a second film, with exactly 

 similar results, by the late Mr. E. W. Newman (of the Westminster 

 Hospital), whose untimely death from blood poisoning, contracted 

 whilst assisting at a necropsy, was an inexpressible loss to his 

 friends and his profession. 



A Simple Wave-length Spectroscope. 



Made to the designs of E. M. Nelson and J. W. Gordon 

 by E. & J. Beck, Ltd. 



This apparatus (fig. 53) has been designed for testing colour screens, 

 but is suitable for many other purposes. It consists of a Thorp's 

 diffraction grating A placed at the centre of a board, on one side 

 of which is placed a slit B. Pivoted on the centre is an arm C, which 

 carries at its end an eye-piece D, in the focus of which are cross 

 wires. The arm C has an index, which reads direct on the scale E 

 in millionths of an inch, the wave-length of the light against which 

 the wires are set. F and G are two lenses, one for collimating 

 the slit B, and the other for focusing to the eye-piece D. 



The chief point of interest about the apparatus is the simple 

 manner in which the scale of wave-lengths is obtained. 



