REACTIONS OF NUCLEI. 151 



From the way in which fibres are formed when the zooids are 

 waslied on a linen filter, it seems probable that fibrinogenic 

 substance may also be present ; but whether this be the same as 

 mucin, oi* what the relation between mucin and the generators 

 of fibrin or myosin, if any such relation exists, is still to be 

 investigated. 



When the precipitate from solutions in alkaL's or NaCl by 

 acetic acid is waslied with acetic acid, then with dilute alcohol, 

 and afterwards dissolved in a small quantity of potash and 

 filtered, the filtrate is generally alkaline, but sometimes neutral. 

 It is unchanged by boiling, gives with mineral acids a precipitate 

 soluble in excess, and with acetic acid a precipitate insoluble in 

 excess. On exceptional occasions, I have seen it, as well as 

 mucin from tendons dissolved by excess of glacial acetic acid, 

 give with acetic acid and ferrocyanide of potassium no turbid- 

 ity, the ferrocyanide of potassium causing any turbidity from 

 the acetic acid to become less and disappear ; but after standing 

 a considerable time a precipitate forms. Chloride of mercury 

 causes no precipitate; with tannin, acetate of lead, or dilute 

 sulphate of copper or chloride of iron it gives a precipitate. 

 Added to potash and sulphate of copper it prevents the pre- 

 cipitation of the hydrated oxide of copper, but the solution 

 remains blue even after boiling. 



Nuclei, freed from stroma by ether and water and then dis- 

 solved in potash, give the same reactions. These reactions 

 differ from those of mucin as given by Eichwald (Kuhne, Lehr- 

 huch der Fliysiologisclien Chemie), inasmuch as tannin, sul- 

 phate of copper and chloride of iron give a slight precipitate or 

 turbidity, but on treating nuclei and mucin from glands and 

 tendons in the same way they give the same reactions. When 

 a salivary gland is treated by potash, and the solution precipi- 

 tated by acetic acid, the precipitate is sticky, and seems to differ 

 much from that given by acetic acid in solutions of nuclei in 

 potash, which is flocky, and gathers on a linen filter into a mass 

 looking like boiled fibrin ; but if the strongly acid and sticky 

 precipitate from the gland be allowed to stand some time in 

 water, it becomes exactly like that obtaiued from the nuclei. 



The zooids and their solution in NaCl act briskly on peroxide 



