The Comparative Physiology of the Pituitary Body 273 



the typical effect, the first injection of extract of posterior lobe can alone 

 be relied upon. Subsequent doses, unless delayed for half an hour, an hour, 

 or longer, according to the amount and strength of the first injection, are 

 followed by a fall of blood-pressure. The same is not the case with regard 

 to the effect upon kidney volume and secretion of urine. 



The force and frequenc}^ of the heart-beat are scarcely affected, but 

 irregularities in the pressure-tracing due to inhibition of the heart are often 

 abolished for a time. 



The kidney expands almost immediately after the injection, and this 

 expansion may be rapid and very considerable, as shown in fig. 5. As was 

 the case after injections of an extract of the posterior lobe of the avine 

 pituitary, the expansion of the kidney may last for twenty minutes or 

 longer and then gradually pass off. The amount of urine secreted begins 

 to increase with the expansion of the kidney, and the increase may be, and 

 usually is, very considerable. In the experiment, of which fig. 5 shows 

 part of the tracing, the increase of urine was from 6 drops in five minutes 

 before the injection to 31 drops in five minutes afterwards, i.e. an increase 

 of five times the amount in a given time. Thei-e may be a delay of several 

 minutes after the injection before any increase of urine is detected, and the 

 same extract has difterent effects in this respect in dift'erent cats. 



The posterior lobe of the pituitary of the cod has, therefore, an action 

 on blood-pressure, kidney volume, and urinary secretion similar to that of 

 the posterior lobe of the mammalian and avine pituitaries. 



Extracts of the posterior lobe of the pituitary of other teleosts, e.g. the 

 ling (Molva vulgaris) and the John Dory (Zeus faber), have been tried and 

 give the same results. One may conclude, therefore, that the posterior lobe 

 of the teleostean pitv^itary, corresponding as it does in structure and in the 

 action of its extracts with the posterior lobe of the mammalian and avine 

 pituitary, has a like function. In the case of the teleost the cells of the 

 pars intermedia predominate in the posterior lobe and are inseparable from 

 the pars nervosa, so that one cannot determine which produces the active 

 material. It seems probable, indeed, that both are concerned ; for, wherever 

 cells of pars intermedia — chromophobe cells of Sterzi — are bound up with 

 pars nervosa, extracts of the resulting tissue produce the effects on blood- 

 pressure, kidney volume, and urine secretion which have been associated 

 with extracts of the posterior lobe of the mannnalian pituitary. 



Saccus Vasculosus. 



Extracts of the saccus vasculosus are practically inactive. There is no 

 efi'ect on blood-pressure, and, although there may be some expansion of tiie 

 kidney, the increase of urine, if any, is very slight (fig. (i). Almost identical 

 efiects are produced by rapid injection of a similar amount of Ringer's fluid. 



It is of interest to note the observation of Gentes, that in difierent 

 species of teleosts the saccus vasculosus varies greatly in size and may even 



