Fundamental Types of Organization. 77 



The brain of the foetus of the mammalia apparently resembles 

 that of the other three vertebrated classes, as the tubercula qua- 

 drigemina of the former, like the posterior hemispheres in the 

 latter, exceed in volume all the other parts. But these posterior 

 hemispheres contain parts which have nothing in common with 

 the tubercula quadrigemina. In the early states of mammalia 

 and fishes there are fissures in the sides of the neck which 

 are somewhat similar to the external branchial orifices of the 

 larva of the frog, tod, and salamander. But the resemblance 

 is merely external. The fissures conduct to no true gills, but 

 to certain small vacuities possessed by the embr)^o of fish in its 

 early states. There is therefore nothing but a mere general 

 analogy in the development of the vertebrata. All analogy 

 ceases whenever we attempt a comparison between the foetus of 

 the latter with the perfect avertebrata. They have no range of 

 ganglia along the abdominal aspect of the body, but have a 

 spinal cord. The circulation is, from the very commencement, 

 totally different from that of the mollusca, crustacea, &c. ; and 

 the organs of sense are, from their first beginnings, quite dissi- 

 milar *. 



But some have gone farther, and maintain, that the higher 

 organs are nothing else than repetitions of the lower organs of 

 the same organism. From which has arisen the doctrine of the 

 " Relative Importance ot Equivalents," &c., which have afford- 

 ed scope enough to the imagination, but have contributed but 

 little to the extension of our acquaintance with the essence of 

 life. 



In my opinion, the following principles must be laid down as 

 the base of every inquiry into the relations between different liv- 

 ing bodies, with respect either to the whole of their organization 

 or their individual organs. 



1. The rank of a living being is higher the more numerous 

 are its points of contact with the external world, the more di- 



• Many other insuperable objections against the doctrine of the develop- 

 ment of organic bodies upon one prototype have been brought forward by 

 Baer^ in his Beilragen zur Kenntniss der niedem Thiere (Verhandl. der Kaiserl 

 Acad, der Naturforsch. xiii. Abth. 2. p. 739> &c.), and in his Etitwickelungt 

 geschichte der Thiere^ Th. i. p. 199. Weber has also very clearly expressed 

 himself on the point in his edition of Hildehrandfs Handbuch der Anatomic det 

 Menschen (i. 125). 



