70 



purpose something else is required, viz. the existence of properties, 

 whose relation with the constituents of blood is to form bone. 

 The same thing is still more clear in the crustaceous ova, as before 

 remarked. 



33. A great apparent difficulty may possibly be started in this 

 place: it may be asked how is it possible for so small a body as the 

 ovum to contain so vast a diversity of properties as is thus sup- 

 posed ? We must answer this question by citing as much as we are 

 able to observe of the nature of properties. 



34. Matter is constituted by a combination of certain proper- 

 ties. No one property is material ; but the aggregate of properties is 

 recognized as that which has a well-known relation with our facul- 

 ties of perception, and which we agree to call matter, just as we 

 agree to call the united existence of an acid and an alkali a natural 

 salt. Now matter itself, in the gross, is said to be infinitely divisible, 

 and yet the individual properties of matter, which are recognized 

 only by a single sense, as its colour or its smell, are constituted by 

 other properties with which we have no perceptive relation at all. 

 (Chap. II. &c.) It may be doubted whether the properties related 

 with smell and vision possess figure; but supposing that properties 

 do possess figure (which is supposing what cannot be invariably true), 

 merely to facilitate our conception of the divisibility of properties, 

 it may be observed (to borrow an illustration) that a substance may 

 continue for a long time to emit an odour sufficient to fill a con- 

 siderable space, without any sensible diminution of its bulk or 

 weight. The odour existing in the minuter spheres of this exten- 

 sive space is of the same nature with the whole; the space may be 

 divided into ten millions of spheres, the property of odour in each 

 of these spheres may be infinitely constituted by other properties, 

 yet all these are emitted from a substance which may perhaps 

 weigh only a single grain. 



35. If then a property is thus divisible, if the property which 

 resides in the smallest perceptible bulk may be divided into ten mil- 

 lions of portions, and each portion comprising an infinity of consti- 

 tuents, we shall have no difficulty in conceiving how a sufficient 

 number of properties for the future development of the animal may 

 reside in an aggregation of matter, as an ovum, which itself appears 

 to consist only of a few particles. 



36. We have said that there is no limit to the diversity of 

 causes, by which the minutest effect is produced, from the necessity 

 of what have been called the causa causarum. It will be allowed, 

 the faculty of vision is as perfect in its kind at a mere point of the 

 retina as it is on the whole surface (there are a thousand instances 

 of the same force if this should be denied), now this faculty is made 

 of many properties; some of them are analyzed in our experiments. 

 There are then, confessedly, many properties 0:1 a scope of matter 

 not bigger than the point of a needle. Now supposing that these 

 properties, instead of remaining combined and minute, as they are, 

 should have a tendency to separate, and being supplied respectively 



