(504 LETTERS. 



LETTER IV. 



In reply to R. Morison, M.D., of Paris. 



ILLUSTRIOUS SIR, The reason why your most kind letter 

 has remained up to this time unanswered is simply this, that 

 the book of M. Pecquet, upon which you ask my opinion, did 

 not come into my hands until towards the end of the past 

 month. It stuck by the way, I imagine, with some one, 

 who, either through negligence, or desiring himself to see 

 what was newest, has for so long a time hindered me of the 

 pleasure I have had in the perusal. That you may, therefore, 

 at once and clearly know my opinion of this work, I say that 

 I greatly commend the author for his assiduity in dissection, 

 for his dexterity in contriving new experiments, and for the 

 shrewdness which he still evinces in his remarks upon them. 

 With what labour do we attain to the hidden things of truth 

 when we take the averments of our senses as the guide which 

 God has given us for attaining to a knowledge of his works ; 

 avoiding that specious path on which the eyesight is dazzled 

 with the brilliancy of mere reasoning, and so many are led 

 to wrong conclusions, to probabilities only, and too frequently 

 to sophistical conjectures on things ! 



I further congratulate myself on his confirmation of my 

 views of the circulation of the blood by such lucid experi- 

 ments and clear reasons. I only wish he had observed that 

 the heart has three kinds of motion, namely, the systole, in 

 which the organ contracts and expels the blood contained in 

 its cavities, and next, a movement, the opposite of the former 

 one, in which the fibres of the heart appropriated to motion 

 are relaxed. Now these two motions inhere in the substance 

 of the heart itself, just as they do in all other muscles. The 

 remaining motion is the diastole, in which the heart is dis- 

 tended by the blood impelled from the auricles into the ven- 

 tricles; and the ventricles, thus replete and distended, are 

 stimulated to contraction, and this motion always precedes the 

 systole, which follows immediately afterwards. 



With regard to the lacteal veins discovered by Aselli, and 



