conversions of related beings. If, then, it be asked why the testes 

 secrete at J6 and did not secrete before; let it be asked as a paral- 

 lel, why a person understands a certain proposition in Euclid at 16, 

 and did not before? The reason is the same: a progressive change 

 or a series of causation leads up to this effect. The character of the 

 changes of mind, each particular phenomenon which it exhibits, is 

 that which it is made by its own constitution or by an external 

 related agent; each change, each phenomenon, whether belonging 

 to the physiology or disease of the body, is produced from similar 

 sources. We have then to discriminate between those things which 

 proceed from the original constitution, or parental radicle, and 

 those which are to be attributed to the influence of externals. 



27. It is demonstrated by our anatomy, that the first per- 

 ceptible original of an animal (as of a man) is an insignificant aggre- 

 gation of matter, possessing no sensible arrangement, but endowed 

 with certain properties. This radicle suffers or exhibits the nume- 

 rous changes which are just represented; but these changes do not 

 occur among its own inherent properties, but in obedience to a 

 relation which subsists between these and certain external properties 

 and substances. The question here then to be discussed is, what 

 share have the properties of the ovum in the subsequent changes 

 which it undergoes! 



28. There are two modes in which the properties of the ovum 

 may contribute towards the conversions which occur in its develop- 

 ment. 1. The first state of the properties of the ovum may be so 

 related with the external as to produce, m conjunction, one change; 

 this change, or this new state, may open a new relation with exter- 

 nals, and produce another change; and so on through a series: 

 in this way, the properties of the original predisposition, or the 

 ovum, may have with respect to subsequent phenomena the impor- 

 tance only of remote causes, and the series and nature of ensuing 

 changes, though taking their determinate character from this first 

 predisposition, may concern principally the accession of properties 

 and substances obtained from the external world. The 2nd mode 

 in which the original properties of the ovum may operate in regard 

 to ensuing changes is by a direct causation with respective pheno- 

 mena; as if that progressive change which has been described went 

 on in properties originally belonging to the ovum, and as if every 

 new change resulted from the development of a latent property, in 

 the manner explained. The latter of these has been preferred (in 

 the instances there cited) in our section on the constitution of the 

 ovum. As we possess no criterion by which we may discriminate 

 when, in particular instances, either of these modes obtains; as also 

 it is probable that in all instances these orignal and external proper- 

 ties are mixed in causation, and the more especially as in our present 

 state of knowledge we may rest satisfied with a deduction from 

 alternatives; on these accounts it appears superfluous to state the 

 objects with which an inquiry for such a criterion might be con- 



