" MOLECULAR COALESCENCE^^ ETC. 239 



phosphate and increase of carbonate ; and in the shells of the 

 invertebrata, where interstitial change does not prevail^ the 

 carbonate alone, or with little phosphate, suffices. In the 

 case of the cod this line of reasoning does not at first proceed 

 so clearly. There is far more phosphate and far less carbo- 

 nate than in the tortoise. The explanation is probably to be 

 found in the nature of the animal matter with which the 

 salts are associated. Throughout the tissues of the ordinary 

 bony fish there is less compactness and tenacity than in the 

 tissues of the higher vertebrata. Any one who has dissected 

 fishes knows hoAV much care is required to avoid laceration 

 of the parts that may be handled freely in a rabbit or a bird, 

 and the very difference exhibited in the matter of firmness 

 by the cooked flesh of birds and the higher animals is to the 

 same eifect. At present I have no distinct information on 

 this point, but I feel justified in suggesting that the remark- 

 able difference in the proportion of the earthy salts is 

 determined by association with a less powerful and charac- 

 teristic colloid, the greatly diminished carbonate still requir- 

 ing a large excess of phosphate to reduce it to docility. 



To one part of Professor Harting's statement much im- 

 portance should, I think, be attached. He asserts that the 

 albumen combines Avith earthy matter, and is transformed 

 into a new substance, or a substance with altogether new 

 reactions, named by him " calcoglobuline." This is probably 

 an illustration of a kind of combination which frequently 

 occurs. For example, some forms new to me having occurred 

 in some electrical experiments, I caused oxalate of copper, in 

 one instance, and carbonate of copper in another, to be pre- 

 cipitated in gelatin. The oxalate formed beautiful green 

 spherules. But in the other experiment no deposit occurred. 

 At the line where the carbonate would be formed in the plug 

 the gelatin was found extremely transparent, of a very bright 

 emerald colour, and almost equal to india-rubber in firmness 

 and resilience ; the sodic side of the plug was softened and 

 purplish in colour ; the cupric side was unchanged. I am 

 inclined to believe that similar alterations of physical pro- 

 perties by combination are the essential conditions in the 

 action of some mineral medicines upon particular tissues, and 

 am at present making this matter a subject of experimental 

 inquiry. 



