FiTCHETT. — Physiological Action of Tut in. 



305 



tralia, and is now the common frog. They were kept till wanted in a large 

 wooden box, in a cool, dark cellar, and supplied with water and fresh grass- 

 sods, but no special provision was made for feeding them. Under these 

 conditions they lived well, and remained healthy. 



Sijmptoms (Exps. 54 to 58 inclusive). — With a lethal dose, the first symp- 

 tom usually noticed was increased frequency of the respiratory movements. 

 To this succeeded lethargy and muscular enfeeblement, the animal crawling 

 in a laboured way, and trailing its hind limbs. If touched now it would 

 attempt to hop, but made little progress from inability to draw the hind 

 limbs completely beneath the body. If left alone it would lie prone on the 

 belly with the limbs extended, and make no effort to move. When con- 

 vulsions occur, as they usually do, though they are not such a marked feature 

 as in mammals, tonic spasms are as a rule more apparent than clonic, and 

 the hind limbs more affected than the fore limbs. Often the animal raises 

 itself rigidly to the full extent of the fore limbs, and opens its mouth spas- 

 modically two or three times in succession. If handled much, or compelled 

 to undergo severe muscular exertion, such as struggling violently to recover 

 the normal position when placed on the back, convulsions appear at once. 

 This recalls the fact that a " tooted " sheep often displays no very obvious 

 symptoms until it is " worked." 



A series of experiments was made to determine the minimum lethal 

 dose (Exps. 36 to 52 inclusive), and the results are presented in tabular 

 form below (Table II). In the early experiments the animals, after receiving 

 the injection, were placed under bell-jars on the laboratory-table. Here 

 they were deprived of moisture, and exposed to a strong light. Under 

 these experimental conditions the results were confusing, frogs with larger 

 doses displaying no symptoms, while animals with lesser doses died. The 

 method was therefore improved upon. Each frog after receiving its in- 

 jection was placed in a small box containing a moist grass-sod in a cool, 

 dark cellar, and a striking uniformity in result was at once obtained. 



Table II. 

 Frogs. — Minimum Lethal Dose. 



Table 11 shows that the highest non-lethal dose attained w^as 10 mlgm. 

 per kilo. Doses of 10-25 mlgm. and over were invariably fatal. Of the frogs 



