ON THE STRUCTURE OF HYALINE CARTILAGE. 7 



the frog and young rabbits (the animals at my disi^osal) 

 were transferred directly to the silver solution, and then im- 

 mediately placed in glycerine, and exposed to sun-light. 

 Fiogs that have died from disease, and especially frogs and 

 rabbits in which a mechanical or other irritation has been 

 applied for several days to the shaft of the lower third of the 

 bone, are best adapted for its demonstration, but successful 

 preparations can also be obtained from healthy animals. 



Fig. 6 represents part of an epithelial surface obtained 

 by this method from a transverse section of the condyle of 

 a frog's femur. In this jDreparation the extent of surface 

 showing the silver markings (all of it has not been shown) 

 is the largest that was obtained. For a short time after it 

 was prepared the nuclei of some of the cells were distinct. 

 The drawing was made a few days after the preparation was 

 mounted (in May, 1875). Since that time the preparation 

 has considerably deteriorated, but it is still (August 21st) 

 perfectly demonstrative to any one at all familiar with silver 

 preparations. The form and arrangement of the cells will 

 be best understood by an examination of the figure, which 

 represents the preparation with great accuracy. 



It is well known that nitrate of silver may produce two 

 distinct results when it permeates a tissue in solution. It 

 may diffuse itself through the ground-substance, which is 

 then stained a varying shade of brown, whilst the interstices 

 which are present in the tissues are unstained, and are l-hen 

 seen as colourless canals and spaces, or it may, while still 

 staining the ground -substance a shade of brown, produce in 

 the system of interspaces, by contact with the lymph-fluid 

 which is present in these channels, an abundant black jive- 

 cipitate of albuminate of silver. 



The spaces and canals Avhich in the former case are indi- 

 cated by their want of colour, are in the latter indicated by 

 the outlines of the black deposit with which they are filled. 

 Both these effects can be produced in hyaline cartilage by 

 nitrate of silver. 



To begin with that in which there are white interspaces 

 in a dark ground. The author has found three distinct 

 kinds of effects so produced, which are respectively repre- 

 sented by Figs. 10, 12, and 14. That represented by Fig. 10 

 will at once recall the white stellate spaces and communi- 

 cating canals seen in a silver cornea. There is a difference 

 to be noted, due, probably, to the unequal permeability of 

 the tissues, rather than to a difference in their relative struc- 

 ture. In a silver cornea the stellate spaces and lines are 

 found at all depths of the substance acted on. In cartilage 



