Letter 4540

[fol. 181] Honoured Sir, Since I had ye Favour of your Letter I have thrice repeated the Experiment of tying up the Aorta descendens with all ye accuracy imaginable, & find that if ye Day be set down immediately after ye Aorta is tied up he can use his lower Parts & walk for a Minute or two, & then Palsy succeeds. This is what I have asserted in my Essay, & I Don’t in ye least dispute ye use fullness of ye Blood towards mucular motion, but I am of opinion its chief use is to distend & keep open the muscular Fibres, & to assist ye Motion of ye Animal Spirits thro’ ye nerves. Mr Cowper assures us that when ye Blood has been intercepted by a Ligature, & ye Muscles have lost their use, he has recovered their Motion again by injecting warm water into the Arteries. Now warm water cannot possibly have any other Effect on ye muscular Fibres than to distend, supple, & relax them, & by its warmth & progressive Motion through ye Arteries it may communicate some Motion to ye Animal Spirits; but it seems impossible for warm water or ye Blood to have any Share in contracting the Fibres. In short, I believe the Blood keeps ye Fibres moist, warm, supple, distended, & every way ready for muscular Motion, & that their Contraction depends upon ye Influx of some subtile Matter from ye nerves, which momentaneously increases ye Force of ye corpuscular Attraction in the Fibres, so as to make their component Particles run closer together. There are many Things which favour this Doctrine, & I hope I have deduced my Theory of muscular Motion from such Principles as will make it appear rational & consistent; though I am far from thinking it is without Faults, & therefore I am willing & ready to correct any of them which my Friends shall advertise me of. I intend to add a Page of two concerning the Laws of Attraction & Repulsion common to all Matter; whereby the Cause of the Elasticity & Contraction of a muscular Fibre may be more fully investigated; & I design to show why a Palsy arises when ye Aorta is tied up, whereby I hope to prove that ye use of ye Blood towards muscular Motion is as abovementioned. After this, Sir, I shall be ready to obey your Commands, & in the mean Time I beg Leave to subscribe myself Your most obedient and most humble servant Browne Langrish Petersfield Septr ye 12th 1732