202 K. E. VON BAER. PHILOSOPHICAL FRAGMENTS. 



But the chief matter is to demonstrate that the most essential 

 peculiarity, the direction of the vital organic current, has a pre- 

 vailing tendency towards the right side. If now this lateral con- 

 trast does not manifest itself in the ingestive and egestive aper- 

 tures, the reason perhaps lies in this, that the plastic body is 

 surrounded by the animal body ; and, therefore, when the former 

 comes to the surface, it is wholly subjected to the type of the 

 latter. The mouth and the anus therefore lie in the median 

 plane of the whole body*. 



If we turn to the internal organs, we must not forget that, 



1 . Almost all organic progression is followed by a retrogression. 

 Were this not the case, a few beats of the heart would drive all 

 the blood out of the body. The question here then is only to 

 state what is the direction of that movement which is the deter- 

 mining one. 



2. That in other cases also the motion can be withdrawn from 

 the direction which originally belongs to it if it possesses a 

 starting-point, which according to the laws of the organization 

 is also the termination of another more powerful organization. 



3. That by the symmetrical influence of the animal part, a 

 current is set up in the median plane of the plastic part. Then 

 if we find a movement at times external to this plane also, but 

 always taking the same direction, we should consider this as the 

 original one. 



These remarks will be rendered more clear by the application 

 which will immediately be made of them. 



If, in the first place, we consider the movement of the blood, 

 we find that in Fishes its principal stream proceeds in the me- 

 dian plane out of the heart, without doubt only on account of 

 the predominance of the animal part, in which respect we must 

 refer to a remark to be made concerning the respiratory apparatus. 



And yet it would seem even here as if the blood desired to go 

 towards the right side, for the ventricle of Fishes appears in 

 general to be more extended towards the left side, and the auricle 

 also lies towards the left. The direction which the blood thence 

 receives is somewhat to the right, but the symmetrical structure 

 of the gills keeps it back in the median plane. In all animals 



* Yet in the larva of the Frog, the anus lies in fact on the right side of the 

 median plane of the tail. 



