85 
was 16. Registration took place by arranging the contrivance 
before the slit of a camera with vertically moving plate, in the 
pencil of light emitted by a projection lantern. 
I experimented chiefly on the cat’s iris. The eye was rapidly 
enucleated and preserved in Tyrode-solution of 37—38° C. Glucose 
soon appeared to have an unfavourable: action, so that tyrode was 
used without glucose. When oxygen was administered the isolated 
iris shortened considerably, but the spontaneous movements were 
much feebler than without the perfusion of O*. In the latter case the 
iris relaxed and spontaneous contractions soon followed. They were 
stronger but of shorter duration than when oxygen had been supplied. 
I found the optimal temperature to be 37°—38°C. All these condi- 
tions being fulfilled, it was not difficult to establish two sorts of 
movements in the iris-preparation. First: movements that were 
comparatively strong, very slow and apparently analogous to those 
known in the literature as “‘tonus-oscillations’. Secondly : movements 
that were much weaker and more frequent, bearing a distinct 
resemblance to what are generally termed: “spontaneous rhythmic 
movements’ of isolated organs. They were not exactly regular, as 
is the case with other organs: their rhythm, as far as we could 
ascertain, varied in normal relations, in Tyrode, from 16 to 29 
contractions per minute. Nevertheless our findings have established 
the capacity of the isolated iris of executing spontaneous, automatic, 
rbythmie coutractions. 8 
Furthermore, [ have dealt with a few pharmacological problems 
viz. that pilocarpin and cholin reinforce these movements as well 
as the tonus-oscillations, whereas adrenalin weakens them and atropin 
inhibits and ultimately abolishes them. Under the influence of pilo- 
carpin the rhythm is accelerated up to 25—38 contractions per 
minute. In the presence of adrenalin the frequency falls to 4—18. 
