animals when fed with lead, and probably explains the fact that many of the experimental animals fed with lead over long periods exhibited no symptoms of poisoning (see p. 85), whereas control animals, given a far smaller quantity of lead by other means and through the lung, rapidly developed symptoms of poisoning. A diversity of opinion exists as to the effect of pepsin upon the solubility of lead. Oliver[14] considers that the pepsin has a retarding influence on the solubility of lead in the gastric juice, and Thomason’s experiments also support this view, although it is difficult to see why the action of _pepsin_ alone should be of such extreme importance. There is also the complicating fact that other added substances in the food may mask any direct pepsin factor that may be present. Albumose and peptone rather than pepsin are to be regarded as the more important substance physiologically in their reaction with lead, and it is interesting to note that Schicksal[15] found that by exposing lead in the form of white lead in a 1 per mille solution of hydrochloric acid in the presence of peptone produced a greater solvent effect on white lead than did the diluted acid alone, and the same effect was also seen on metallic lead. TABLE II.--SCHICKSAL’S TABLE. +--------------------------------+---------------+------+-----------+ | | | | Amount | | | | | dissolved | | | | |returned as| | | | | Metallic | | Solution. | Substance. | Time.| Lead. | +--------------------------------+---------------+------+-----------+ |(_a_) 1·0 per cent. peptone}100 |{White lead, |3 days|0·1471 grm.| | 0·1 per cent. HCl }c.c.|{10 grms. | at | | | | |37° C.| | |(_b_) 1·0 per cent. peptone}100 |{Metallic lead,| „ |0·0330 „ | | 0·1 per cent. HCl }c.c.|{4 grms. | | | | | | | | |(_c_) 0·1 per cent. HCl, 100 |White lead, | |0·0983 „ | | c.c.|10 grms. | | | | | | | | |(_d_) 0·1 per cent. HCl, 100 |Metallic lead, | |0·0194 „ | | c.c.|4 grms. | | | | | | | | |(_e_) 0·3 per cent. Na₂CO₃ |Metallic lead, | | None | | |4 grms. | | | | | | | | |(_f_) 0·3 per cent. Na₂CO₃ |White lead | | „ |