205 
exact and comprehensive and is as follows: “It will be perceived that the 
blood poured into the right auricle is mostly impure or venous, that poured 
into the left fully aerated or arterial. When the auricles contract, which 
they do simultaneously, each passes its blood into the corresponding part 
of the ventricle, which then instantly contracts before the venous and ar- 
terial bloods have time to mix. Since the conus arteriosus springs from 
the right side of the ventricle, it will at first receive only venous blood, 
which, on contraction of the conus, might pass either into the bulbus aortae 
or into the aperture of the pulmo-cutaneous trunks. But the carotid and 
systemic trunks are connected with a much more extensive capillary sys- 
tem than the pulmo-cutaneous, and the pressure in them is proportionately 
great, so that it is easier for the blood to enter the pulmo-cutaneous trunks 
than to force aside the valves between the conus and bulbus. A fraction 
of a second is, however, enough to get up the pressure in the pulmonary 
and cutaneous arteries, and in the meantime the pressure in the arteries 
of the head, trunk, ete., is constantly diminishing owing to the continual 
flow of the blood toward the capillaries (sic). Very soon, therefore, the 
blood forces the valves aside and makes its way into the bulbus aortae. 
Here again the course taken is that of least resistance; owing to the 
presence of the carotid gland the passage of blood into the carotid trunks 
is less free than into the wide elastic systemic trunks. These will there- 
fore receive the next portion of blood, which, the venous blood having 
mostly been driven to the lungs, will be a mixture of venous and arterial. 
Finally, as the pressure rises in the systemic trunks, the last portion of 
blood from the ventricle, which, coming from the left side, is arterial, will 
pass into the carotids and so supply the head.” 
It will be seen on critical examination of this scheme that several 
points are open to argument even if we grant the segregation of bloods in 
the spongy ventricle: 1, the element of time; 2, the mechanics; 3, the com- 
parative anatomy ; and 4th, the experimental evidence. 1. The frog’s heart 
under normal conditions beats about 60 to the minute with a ventricular 
systolic phase of about 0.2 sec. Now if one reads the description, bear- 
ing in mind that the whole process is completed in one-fifth of a second, 
and that all this is inferred in order that the head shall receive a better 
blood supply, one is tempted to hold one’s breath. The time is short and 
much must be accomplished. If the blood in the systemic arteries is being 
forced toward the capillaries, what is holding it back in the pulmo-cu- 
taneous and carotid trunks? Again the regulation of the valves and re- 
