'Notes, ii. ip. 175 



as to the brain : firstly, that it only occupies the front portion of the skull, there 

 being an. empty space behind it ; secondly, that it is entirely destitute of blood- 

 vessels ; and, 'thirdly, that it is cold to the touch. For the two first of these 

 it is perhaps unfair to hold A. as directly responsible, seeing they are both to be 

 found in Hippocrates [Kiihn^s edit. i. 683, iii. 349), and may have been accepted by A. 

 on his authority without personal examination into the matter. Still A. did. undoubtedly 

 himself examine the brains of some animals, and we have to consider how a man who 

 was certainly no utterly mean observer can have reconciled what he learnt from authority 

 with what he saw himself. I suspect that the explanation is to be found in his having 

 only examined, and that imperfectly, the brains of fishes, tortoises, and other cold- 

 blooded animals. For while it is certain" that he did examine the brains of such animals, 

 there is no clear sign of his having examined the brains of any warm-blooded animal, 

 at any rate in a fresh conditionj though he inay very possibly havo examined them after 

 cooking, a process to- which he seemingly had resort (cf. ii. 7, 16), with the idea 

 of hardening them. Admitting this supposition to be correct, we can see how his 

 errors may have originated. For in Fishes and Reptiles the brain is not large enough 

 to fill the cranial cavity, a character to which Lamarck attached great importance in 

 distinguishing these groups from Mammails and Birds '(/'>4?7. Zool. i. z'jiy. Martinis edit.). 

 In the tortoise, for instance, the area- of a vertical section of the b'rain, according to 

 Desmoulins {Todd's Cycl. i. 724), is nearly a third less than the area of the cavity. 

 So also the brain completely fills the brain-case in embryonic fishes, but in the adult 

 only occupies a. small part of it, as its growth is by no means proportionate to that of 

 the cranium itself. That A. had noticed this is highly probable from his saying (Z?. G. 

 ii- 6, 35) that the brain of animals is at first of large size, but afterwards falls in and 

 becomes of smaller dimensions. So also in Cephalopods, animals specially studied by 

 A., and with whose so-called brain he was acquainted, the cavity in which the ganglia 

 arQ lodged is much larger than the ganglia themselves. 



So much for the first error. Now for the second. The brain does as a' matter of 

 fact receive a very large amount of blood ; but by far the greatest part of this goes to 

 the superficial gray matter.. All this superficial blood A. reckoned as belonging to the 

 Pia mater, which he describes sis highly vascular. Either he did not see that the small 

 vessels were prolonged from this into the superficial brain-substance, or more probably 

 he considered this superficial substanc^, differing as it does from the mass below in 

 colour and. general aspect, to be part of the Pia mater itself, from which in fact he can 

 hardly have learnt to separate it mechanically. That this was really the view of the 

 Pia mater entertained by the ancients of his time is, I think, confirmed by the fact, 

 that when the nerves had afterwards been distinguished from' other white structures, 

 Erasistratus still maintained for many years that they ended in the Pia mater. It 

 seems inconceivable that lie can have so thought, unless he included in the Pia mater 

 the superficies of the brain itself. There are, however, numerous small vessels in that 

 white mass, which A. regarded as exclusively the brain. These are so «mall that on 

 section they appear only as bloody puncta, and are so barely visible in the brains of 

 fishes and tortoises, that they might easily escape notice. In the brain of a mammal 

 they are more apparent ; but if we imagine, as I have suggested, that A. only examined 

 sucji brains when cooked, they would have been quite invisible to him. Even had he 

 seen them, I do not think that, considering their minuteness and the general bloodlessness 

 of the part when compared with other organs, he would have attributed any importance 

 to their presence. The contrast in amount in the two cases would have seemed sufficient 

 to warrant him in speaking of the one organ as full of blood, and of the other as having 



