468 Prof. A. B. Macallum. Detection and Localisation 



molybdate occur, but a brown colour in other parts of an intensity 

 which varies according to the length of time during which the pre- 

 paration is washed, but if it is long and continuously treated with 

 water no brown colour appears. The brown, therefore, would be due 

 to molybdate of ammonium, and is no indication of the presence of 

 the phosphorus compound. 



Heine* was unable to confirm Raciborski's observations regarding 

 the reaction produced by pyrogallol, but he found, using stannous 

 chloride as a reducing agent, that almost invariably a blue reaction 

 appeared, which may pass eventually into a dirty green colour. In 

 the test-tube also the reaction with the reducing agent is, according* 

 to the amount of the molybdate present, as well as to the strength 

 of acidity in the fluid, a green, brown, or blue one, whether phosphates 

 are present or not. 



Pollacci,t using zinc chloride as a reducing reagent, found the 

 resulting colour range from dark blue to grey. 



It is evident from the foregoing that there is error somewhere in 

 the observations which have been made on the action of pyrogallol 

 on ammonium phospho-molybdate, and it is obvious that, if Ra9i- 

 borski is right in his contention, then the results of the investigations 

 of Lilienfeld and Monti, relying as they did upon the "yellow, brown, 

 or black " reaction to indicate the presence of phosphorus, must be 

 wrong. As a number of observers, including Sherrington,* Gourlay, 

 and Held, || have used the same method and the same criteria on 

 special tissue elements, it is therefore important to know the truth 

 concerning the results so obtained. 



My observations confirm Raciborski's on the action of pyrogallol 

 on ammonium phospho-molybdate. When the former, in solution, 

 aqueous or ethereal, is allowed to act on the thoroughly washed 

 phospho-molybdate precipitate, the canary yellow of the latter is inva- 

 riably turned to green, even in the presence of nitric acid, and this 

 colour is maintained for a couple of hours, after which the precipi- 

 tate takes up slowly a darker shade, until at the end of twenty-four 

 hours it has a black colour with a faint shade of green in thin layers. 

 The form of the crystals, which are black, is maintained. When the 



* " TJeber die Molybdansaure als mikroskopischer Eeagens," ' Zeit. fur Physiol. 

 Chemie,' vol. 22, p. 132, 1896-97. 



f "Sulla distribuzione del fosforo nei tessuti vegetal!," 'Malpighia,' vol. 8, 1894; 

 Abstract in ' Zeit. fur Wiss. Mikrosk.,' vol. 11, p. 539. 



J " Koto on some Changes in tbe Blood of tbe general Circulation consequent 

 upon certain Inflammations of acute and local character," ' Roy. Soc. Proc.,' vol. 55, 

 p. 161, 1894. 



"Proteids of the Thyroid and Spleen," 'Journ. of Physiol.,' vol. 16, p. 23, 

 1894. 



|j " Beitrage zur ^tructur der Nervenzellen und ihrer Fortsatze," ' Arch, fur Anat. 

 und Phys.,' Auat. Abthg., 1895, p. 396. 



