EFFECTS OBSERVED IN THE WHOLE ANIMAL 951 



constitution, vitamin intake, electrolyte balance, protein nutrition, and 

 other imponderables. The concentrations of mercury in the blood or urine 

 are, of course, not the critical determinants in poisoning when the mercury 

 has been slowly taken into the body over a period of months or years. 

 Mercury is picked up by the various tissues at different rates and to dif- 

 ferent degrees, and it is the eventual levels of mercury in these tissues which 

 determine the toxic response. Such accumulation may occur over a long 

 time and several weeks be required before a balance between intake and 

 excretion is achieved. One factor which must be of importance, but about 

 which little is known, is the concentrations of the various thiols in the blood, 

 since this will not only alter the over-all tissue uptake but will modify the 

 pattern of distribution in the body. Most mercurialism in adults is industrial 

 in origin and due to the inhalation or ingestion of small amounts of metallic 

 mercury or mercury compounds daily over a prolonged period. 



General Symptoms of Mercury Poisoning 



We have discussed the most im])ortant aspects of acute poisoning by the 

 inorganic and organic mercurials, namely, the effects on the cardiovascular 

 and renal systems, and little more need be added. Slow inhalation of mer- 

 cury vapor produces typical poisoning of the kind commonly seen with the 

 inorganic mercury salts, because the metallic mercury is oxidized during 

 and after absorption. However, when the concentration of mercury vapor 

 is high, absorption is faster than oxidation and unique symptoms are ex- 

 hibited, e.g., hyperthermia, tachypnea, cough, nausea, dizziness, and weak- 

 ness (Carpenter and Benedict, 1909). These may be due primarily to the 

 greater uptake of mercury by the central nervous system under these con- 

 ditions. It is important to emphasize that the character of mercury poison- 

 ing depends greatly on the tissue distribution, and hence on the physico- 

 chemical properties of the mercurial. Thus the more or less volatile, lipid- 

 soluble, alkyl mercurials produce quite a different picture from the inor- 

 ganic or diuretic mercurials (Miiller et al., 1911; Hunter et al., 1940). Alkyl 

 mercurials act rather selectively on the central nervous system to produce 

 ataxia, paralysis, and depression — in higher concentrations they act much 

 like certain anesthetics — and acutely these effects are possibly unrelated 

 to mercury or reactions with SH groups. 



The acute effects of mercurials on the central nervous system are often 

 marked but have not been analyzed in detail. When HgCL, is injected sub- 

 cutaneously into rats at the high dose of 17 mg/kg, there is progressive loss 

 of the reflexes and all have disappeared after 54 hr, this being reversible 

 upon administration of a Hg++-binding thiol (Galoyan and Turpaev, 1958). 

 Conditioned reflexes are suppressed partially at the much lower dose of 

 3.7 mg/kg (Galoyan, 1957). The respiration is usually affected and may be 

 taken as an index of certain central actions. Respiratory stimulation by 



