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14. There are some properties of the organic spirit (indeed 

 the principal part of them), which are common both to the male 

 and female: these may be called perfect resemblances: there are 

 others which are different, or their efficient union is different, 

 though bearing a resemblance in some respects; and there are 

 others which bear no obvious similitude. These properties in the 

 parents reside, according to the restrictions and alternatives be- 

 fore proposed, one set in the maternal ovum, and the other in the 

 seminal fluid, and it is in these productions that we are now called 

 upon to consider them. 



15. The instances of the first, viz. those of perfect resemblance, 

 are found in the properties which develop common identical sub- 

 stances, as bone, brain, muscle, &c. in which the properties 

 derived from both parents agree perfectly to a certain extent; 

 those of the second, viz, where there is agreement in a general 

 character, but difference in some respects; as in the allied pro- 

 perties with the common ones just mentioned, which modify the 

 development of bone, brain, muscle, &c.; those of the third, viz. 

 properties that are totally differential, as those which develop the 

 organs of generation and those which supply, on either side, the 

 seeds of hereditary disease. 



16. These properties on both sides are related according to 

 spiritual laws. But, in general agreement with the laws of causa- 

 tion, they may be classed under three heads: 1st, properties of 

 aggregation: these include the perfect resemblances; 2nd, pro- 

 perties of constitution, as where differentials unite and modify 

 each other; and, 3rd, properties differential, holding with regard 

 to the others neither the relation of aggregation nor that of con- 

 stitution, but which preserve singly their own natures. 



17. It has been said that these rudiments of the future ani- 

 mal contain the properties which afterwards produce bone, &c. 

 that is, that these properties are not conferred from without. 

 But a question was started at the same time, viz. whether these 

 are precisely the properties which are to form bone, &c. or 

 whether they are only predisponent, and made perfect by ex- 

 ternal relations* It was also said the former would be presumed 

 upon to a certain extent, and I now repeat more fully the ground 

 of that presumption. The fecundated ovum of an oviparous 

 animal is consigned perhaps to a dunghill or the sand ; it obtains 

 here no accession of properties except heat, and a series of inter- 

 nal changes take place, which terminate in the formation of the 

 textures, &c. of the foetus, which are, in their nature, nearly those 

 of the adult. Now if a property to form muscle, another skin, 

 another bone, another stomach, &c. existed merely in a predisponent 

 state in the fecundated ovum; that is, not the perfect property, a 

 deficient identity, this one cause, viz. heat, could not supply to all 

 the deficient properties those differentials, agreeing in number, 

 which would render each perfect. For this would be to suppose 

 what indeed is possible according to the laws of causation, but of 

 which we have no single instance; it would be to suppose that 



