On Anlmnl Fluids. 299 



3. Sulphate of potash. That a sulphate exists T per- 

 ceived in my experiments, and have accordingly inserted it 

 among the sahne matters in my pubhshed papers ; but that 

 it is s'jlphate of potash I apprehend will iiot be allowed 

 to have been sliown by Dr. Marcet. 



4. Phosphate of lime, of iron, and of viagnesia, are 

 enumerated in the memoir before me. Of phosphate of 

 lime there is good evidence, as I have set forth, and coincide 

 in my results with those of the author, as well as that there 

 is probably phosphate of magnesia; also that there is iron : 

 but I was not able to infer that it was in the stale of phos- 

 phate, [ only inserted it in my results as an oxide. Al- 

 though it is not essentially connected, it may be useful to 

 refer to a process which I offer as evidence against the com- 

 mon opinion that the red and black colour of the blood is 

 owing to iron. I have mentioned it in mv lectures during 

 some past vears. The result is published in the Edinburu;h 

 Medical and Surgical Journal, vol. vii. p. 124, for January 

 18J I. I collected 1 !0 grains of the red part of blood in a dried 

 state, by repeated ablutions from 10 000 grains or upv/ards 

 oftv.enty (uincts of blood. By burning in a platina cru- 

 cible it afforded, in weight, two grains and a hali of a half- 

 fused brown tasteless substance. By boiling in muriatic 

 acid a part was dissolved. This solution was not stvptic 

 to the taste; it became blackish on adding tincture of eall 

 nut, and on adding prussiate of potash it afforded a d^ep 

 blue coloured precipitate, which did not vield on ignition 

 above half a grain of reddish brown powder. Is it then 

 probable that twenty ounces of blood should derive rts co- 

 lour from half a grain of oxide ot iron? I think proper to 

 speak of this result, at this time, because it was pubhshed 

 anonvmously, and because subsequently to its publication 

 I llnd it has been mentioned by other persons without ac- 

 knowledgement ; perhaps from not knowing this circum- 

 stance. 



5. I found also indications of carlonale of lime and of 

 silica not enumerated by Dr. Marcet. Future experiments 

 must however lurnish unequivocal evidence. 



Muiiaie of pota-.h inserted by the author instead of 

 potash unit fid to animal matter, or tf» some other destructi- 

 ble -jiibaiance as I have inferred. On this question perhaps 

 more than necvssary has been already said in the present 

 and tormcr papers. 



7. SuL'carlonate of soda asserted by the author has been 

 the subject of I'.iscussioa at the same time as the last- men- 

 tioned ingredient. 



U 2 8. Muriate 



