14 DR. G. THIN. 



nuclei. It was impossible not to observe the identity of ap- 

 pearance with that of the bodies described as giant cells or 

 myeloplaques. By a careful examination the presence of 

 similar bodies on both surfaces, and in the thickness of the 

 sealed cartilage, could be detected. A drawing of one of 

 the free " giant cells " seen lying close to the edge of the pre- 

 paration is given in Fig. 18. 



The curious part of the history is what follows : — The pre- 

 paration, with others, was taken from the author's house to 

 Dr. Ewart's room in the museum of University College, and 

 must have remained essentially unchanged there for more 

 than twenty-four hours, as the day after he had received the 

 preparations Dr. Ewart was able to demonstrate the struc- 

 tures in question to Professor Ray Lankester. During the 

 following week the preparation remained in the same 

 room, but was not further examined. It was then brought 

 back to the author, and again examined by Dr. Ewart and 

 himself. To their astonishment every trace of the giant 

 cells had disappeared. The fluid contained threads of 

 streaky looking protoplasmic substance, and swarmed with 

 bacteria, in active motion, in the forms known as coccos, 

 rods, and leptothrix. 



The development of bacteria in the preparation took place 

 whilst it was iu University College. This, be it remembered, 

 was in the end of July, the preparation having been sealed 

 in tlie middle of December. 



It is well to add that the section of cartilage was from a 

 full-grown sheep, and quite clear of the bone. 



One other preparation remains to be described. A pin 

 was pushed through the knee-joint of a frog from side to 

 side between the femur and tibia, the cartilage not being 

 injured further than would result from the presence of the 

 smooth foreign body in the joint. After seven days the frog 

 was killed, and the condyle of the femur placed for three days 

 in a quarter-per-cent. solution of osmic acid. Transverse 

 sections were then made and mounted in glycerine. Thin 

 sections only were sufficiently transparent. The colouring 

 was found to be unequally distributed. Broad winding 

 tracts, darkly stained, contrasted with comparatively faintly 

 stained intermediate portions, and what Avas especially note- 

 worthy, the coloured tracts contained the ordinary carti- 

 lafre- cells. The intermediate faintly stained, homogeneous- 

 looking substance contained no visible cells, and indicated 

 by an appearance of splitting the described division of car- 

 tilage into polygonal areas. 



The deeply stained cellular areas and lightly stained in- 



