MULTIPLIED ORGANIC EFFECTS. 43 



indirect evidence, we may pretty safely reach the conclu- 

 sion that here too the law holds. 



Observe, first, how numerous are the effects which any 

 marked change works upon an adult organism — a human 

 being, for instance. An alarming sound or sight, besides 

 the impressions on the organs of sense and the nerves, may 

 produce a start, a scream, a distortion of the face, a tremb- 

 ling consequent upon a general muscular relaxation, a 

 burst of perspiration, an excited action of the heart, a 

 rush of blood to the brain, followed possibly by arrest of 

 the heart's action and by syncope : and if the system be 

 feeble, an indisposition with its long train of complicated 

 symptoms may set in. Similarly in cases of disease. A 

 minute portion of the small-pox virus introduced into 

 the system, will, in a severe case, cause, during the first 

 stage, rigors, heat of skin, accelerated pulse, furred 

 tongue, loss of appetite, thirst, epigastric uneasiness, 

 vomiting, headache, j)ains in the back and limbs, muscular 

 weakness, convulsions, delirium, &c. ; in the second stage, 

 cutaneous eruption, itching, tingling, sore throat, swelled 

 fauces, salivation, cough, hoarseness, dyspnoea, &c. ; and in 

 the third stage, (edematous inflammations, pneumonia, pleuri- 

 sy, diarrhoea, inflammation of the brain, ophthalmia, erysipe- 

 las, &c. : each of which enumerated symptoms is itself more 

 or less complex. Medicines, special foods, better air, might 

 in hke manner be instanced as producing multiplied results. 



Now it needs only to consider that the many changes 

 thus wrought by one force upon an adult organism, will be 

 in part paralleled in an embryo organism, to understand 

 how here also, the evolution of the homogeneous into the 

 heterogeneous may be due to the production of many 

 effects by one cause. The external heat and other agen- 

 cies which determine the first complications of the germ, 

 may, by acting upon these, superinduce further complica- 

 tions ; upon these still higher and more numerous ones ; 



