260 



Dr. F. W. Pavy on 



[Jan. 16, 



in hyaline cartilage, whether the latter existed as a normal structure, 

 or as a pathological growth. They further show that, taken alone, 

 carmine or eosin staining should not be held as conclusive evidence of 

 the existence or limits of cellular protoplasm in any animal tissue. 



EXPLANATION OF THE PLATE. 



(All the figures are drawn by camera lucida ; magnifying power x 2G0.) 



Hyaline Caetilage. 



Figure 11. The normal structure of hyaline cartilage. Purpurine. 

 Figure 12. Isolated cells. Osmic acid. 



Figure 13. Isolated nuclei adherent to portions of cartilage substance, simulating 

 branched cells with fibre-processes. Bichromate of potash ; logwood. 



Figure 14. Stained substance in the cartilage simulating branched cellular proto- 

 plasm. Bichromate of potash ; eosin. 



Figure 15. Fragments of cartilage substance separated by needles. Purpurine. 



III. " Volumetric Estimation of Sugar by an Ammoniated Cupric 

 Test giving Reduction without Precipitation." By F. W. 

 PAVY, M.D., F.R.S. Received December 5, 1878. 



To be able to effect the quantitative determination of a body with 

 accuracy and facility is an important matter looked at in relation to 

 the study of its bearings. In the case of sugar there are no reliable 

 means of precipitating and weighing it, either alone or in combina- 

 tion, and thus in the chemical estimation of this principle an indirect 

 method has to be resorted to. The only property upon which depend- 

 ence can be placed, for the purpose of chemical quantitative analysis, is 

 its reducing action, under the influence of heat, upon certain metallic 

 oxides, and that of copper is the one which general experience shows 

 to answer best. 



In the ordinary volumetric application of the copper test, the pre- 

 cipitation and diffusion of the reduced suboxide through the liquid 

 interferes with the clear perception of the precise point of complete 

 decoloration, and thus detracts from its delicacy. For purposes 

 where minute accuracy is of no moment, a sufficiently approximate 

 result can be obtained, but for physiological investigation, and in 

 other cases where precision is indispensable, the process is quite unfit 

 for employment. 



With the view of obtaining increased accuracy, chemists have had 

 recourse to the plan of collecting the precipitate of reduced suboxide 

 and weighing it as such or after reconversion into the oxide. From 

 the difficulty, however, that exists in procuring the metallic oxide in a 

 pure and uniform state, and from the impossibility of completely 

 freeing the filter paper used from adhering surplus copper solution, 

 some uncertainty is given to the results obtained by this method. To 



