TRACE ELEMENTS IN ANIMALS - 125 



method are concerned Webb's results are in general agreement 

 with those of Fox and Ramage. Copper and strontium were 

 found in every animal examined, while manganese was detected 

 in all except two of the species examined. Lithium was found 

 to be widely distributed, although Webb was of the opinion 

 that the concentration of this in the tissue fluids is never higher 

 than it is in sea water. Cobalt was found in only one species, 

 the gastropod Pleurobranchus plumula, while nickel was definitely 

 found only in this and one other species, also a gastropod. It 

 should be pointed out that neither cobalt nor nickel has been 

 detected in sea water so that the concentration of these ele- 

 ments in the environment must be exceedingly low. Silver, 

 lead and cadmium were found to be fairly widely distributed 

 and the same was found for barium, which Fox and Ramage 

 had been unable to detect in any of the specimens they exam- 

 ined. This, and the greater incidence of cadmium as established 

 by Webb, may be due to the greater sensitivity of the arc 

 method employed by the latter as compared with the flame 

 method of Ramage. 



As regards elements not detectable in small quantities by the 

 flame method a measurable amount of boron was found in every 

 species except two, while aluminium was detected in nine out of 

 twenty species examined. Silicon was found in a number of 

 species, but Webb concluded that apart from those in which 

 there is a siliceous skeleton there is little tendency for the 

 accumulation of this element. Chromium was found in four 

 species, but unfortunately the data obtained for molybdenum by 

 Webb are regarded as of uncertain value on account of the pos- 

 sibility of its presence in the electrodes used. Zinc in com- 

 paratively large quantities was found in some species, though in 

 others this element was not detectable, while tin was found in 

 small amount in several of the species examined. Fluorine in 

 quantity was found in two gastropods. Vanadium is of interest 

 because it is known to occur as a pigment in the blood of the 

 ascidians (Henze, 1911). It appears, however, to be generally 

 absent in recognizable amount from animals of other groups, the 

 only example of an animal other than an ascidian in which Webb 

 found it being the mollusc Pleurobranchus plumula. Finally, 

 there is a group of elements for which Webb searched but which 



