GENERATION. SECT. XXXIX. 4. 6. 



either of their bodies. Some of thefe hereditary difeafes are 

 (imply owing to a deficient activity of a part of the fyftem, as of 

 the abforbent veffels, which open into the cells or cavities of the 

 body, and thus occafion dropfies. Others are at the fame time 

 owing to an increafe of fenfation, as in fcrofula and confump- 

 tion , in thefe the obftrudion of the fluids is firft caufed by the 

 inirritability of the veflels, and the inflammation and ulcers 

 which fucceed, are caufed by the confequent increafe of fenfa- 

 tion in the obftruded part. Other hereditary difeafes, as the 

 epilepfy, and other convulfions, confift in too great voluntary 

 exertions in confequence of difagreeable fenfation in fome par- 

 ticular difeafed part. Now as the pains, which occafion thefe 

 convulfions, are owing to defect of the action of the difeafed 

 part, as (hewn in Seel:. XXXIV. it is plain, that all thefe heredi- 

 tary difeafes may have their origin either from defective irrita- 

 bility derived from the father, or from deficiency of the ftimu- 

 lus of the nutriment derived from the mother. In either cafe 

 the effect would be fimilar ; as a fcrofulus race is frequently 

 produced among the poor from the deficient (limulus of bad 

 diet, or of hunger ; and among the rich, by a deficient irritabili- 

 ty from their having been long accuftomed to too great ftimulus, 

 as of vinous fpirit. 



6, From this account of reproduction it appears, that all ani- 

 mals have a fimilar origin, viz from a fingle living filament ; 

 and that the difference of their forms and qualities has arifen 

 only from the different irritabilities and fenfibilities, or volunta- 

 rities, or aflbciabilities, of this original living filament ; and per- 

 haps in fome degree from the different forms of the particles of 

 the fluids, by which it has been at firft Simulated into activity* 

 And that from hence, as Linngeus has conjectured in refpect to 

 the vegetable world, it is not impoffible, but the great variety of 

 fpecies of animals, which now tenant the earth, may have had 

 their origin from the mixture of a few natural orders. And 

 that thofe animal and vegetable mules, which could continue 

 their fpecies, have done fo, and conftitute the numerous families 

 of animals, and vegetables which now exifl , and that thofe 

 mules, whicfy were produced with imperfedt organs of genera- 

 tion, perifned without reproduction, according to the obferva- 

 tion of Ariftotle ; and are the animals, which we now call mules. 

 See Botanic Garden, Part II. Note on Dianthus. 



Such a promifcuous intercourfe of animals is faid to exift at 

 this day in New South Wales by Captain Hunter, And that 

 not only amongft the quadrupeds and birds of different kinds, 

 but even amongft the fifh, and, as he believes, amongft the 

 vegetables. He fpeaks of an animal between the opoffum and 



the 



