$ 2 GENERATION. Sect. XXXIX. 4. 6, 



either of their bodies. Some of thefe hereditary difeafes are 

 limply owing to a deficient activity of a part of the fyftem, as of 

 the abforbcnc veflels, which open into the cells or cavities of the 

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

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

 ticn ; in thefe the obftruction of the fluids is firft caufed by the 

 inirritability of the veiTels, and the inflammation and ulcers 

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

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

 epilepfy, and other convulfions, confiib in too great voluntary 

 exertions in confequence of difagreeable ienfation 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 fhewn 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- 

 Jns of the nutriment derived from the mother. In cither cafe 

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

 produced among the poor from the deficient ftimulus 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 ic 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 alTociabilities, 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 itimulated into activity. 

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

 the vegetable world, it is not impoihble, but the great variety 1 

 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 conltitute the numerous families 

 of animals and vegetables which now exit! ; and that thofe 

 mules, which were produced with imperfect organs of genera- 

 tion, perifhed without reproduction, according to the obierva- 

 tion of Ariftotle ; and are the animals, which we now call mult* 

 See Botanic Garden, Part II. Note on Dianthus. 



Such a promifcuous intercourfe of animals is faid to exiit at 

 this day in New South "Wales by Captain Hunter. And that 

 not only amongft the quadrupeds and birds of different kiucb, 

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

 vegetables. He fpeaks of an animal between the opofium and 



th 



