208 Notes, iii. 7—8. 



15. A. assigns two main functions to the spleen ; one, to assist by its heat in the 

 concoction. of the food ; the other, to withdraw superfluous humours from the stomach. 

 When these offices can be adequately performed without the aid of a spleen, then this 

 organ is of small size. Thus in birds the stomach is hot enough to effect concoction by 

 itself, and there is an adequate outlet in the skin for the superfluous humours. In birds 

 then the spleen is^mall. So also with other ovipara. In fact in these animals the spleen 

 exists for no actual use ; but simply to fulfil the law of symmetrical development, which 

 requires some counterpart to the liver. 



Such was A.'s idea of the spleen. The notion of its serving to attract superfluous 

 hiamours was taken from Hippocrates, who thus expresses himself, " I say that, when a 

 man drinks a more than- ordinary amount of .fluid, both the body and the spleen attract to 

 themselves the water from the stomach " (De Mortis, iv. 9). And again, " When a person 

 has fever and violent thirst, and drinks copiously without vomiting, a part of the fluid 

 passes into the bladder and is expelled as urine ; but the rest is taken by the spleen, 

 which attracts it from the stomach, being of a porous and spongy texture, and lying cloee 

 to the stomach " {De Morb. Mul. i. 15). 



This notion was actually revived by Sir E. Home, who .imagined that when fluid was 

 drunk much of it passed from the cardiac end of the stomach by some unknown channel 

 directly to the spleen. This view, however, he afterwards abandoned. See Phil. 

 Tram. 181 1. 



16. " In those that drink marsh- water the spleen always becomes enlarged, and the 

 belly hard." — Hippocrates. 



17. A bladder-like lung is to A., owing to the small amount of fluid it contains, an 

 indication of scanty fluid in the body generally. See next chapfer. 



18. A. thought that the bladder was the essential agent in forming the urine, and the 

 kidneys m«re adjuncts, though he also admits that when the fluid leaves- the kidney, it 

 already has in a measure the characters of an excretion. Cf. iii. 9, 7. A.'s 'error was 

 corrected by the time of Galen i^De Usu part. 5, 5). 



19. Namely from above downwards ; an upper position implying 'generally superiority 

 in other respects. Cf. iL 2, Note 6. 



(Ch. 8.) 1. i.e. the Mammalia (cf iii. 6,' Note 9). As a matter of fact birds have no 

 bladder, and yet highly vascular lungs ; but their real lungs escaped A.'s notice. Cf. iii. 6, 

 NotQ 10. 



2. A. distinguishes the scales of fishes from those of reptiles by giving them distinct 

 names, but nowhere discusses their differences ; excepting that he says, " these plates are 

 equivalent to scales, but of a harder character." Cf iv. 11, Note 14. 



As regards the formation of scales, and similar parts, his notion was this. The blood 

 passes from the heart to all parts of the body by the vessels. At last it reaches their 

 ultimate twigs. As none of it returns to the heart, it must here be disposed of in some 

 way or other. That in the internal vessels is converted into the substance of the viscera 

 (cf iii. 7, Note 8) ; that in. the external vessels oozes out as sweat, or is converted into 

 various integumental structures, nails, hairs, scales, feathers. But when there is loo 

 much blood for its excess to be thus got rid of, or when the integument is such as not to 

 allow of transpiration, some other means of disposal are required, and these are furnished 

 by the presence of urinary organs. Bacon (A'a/. Hist. § 680) expresses a similar opinion. 



3. !Both here and in other passages it is stated that Mammalia alone have an urinary 

 bladder, with the exception of tortoises. The facts are these. AIL Mammalia have a 

 true bladder developed from the allantois, directly continuous with the ureters (Mono- 

 tiemata excepted), and serving for the reception of urine and for this alone. 



