An Account of Dr. Trew's Dissertation Concerning the Differences of a Human Body before and after Birth

VII. An Account by David Hartley, M.B. F.R.S. of Dr. Trew's Dissertation concerning the Differences of a Human Body before and after Birth, intituled, Diss. epistolica de differentiis quibusdam inter hominem natum & nascendum intervenientibus, deque vestigiis Divini Numinis inde colligendis. Jo. Georgio Kramero inscripta. Cum Iab. Æn Autore Christoph. Jacobo Trew, Noribergiae, 1736. 4to. There are, according to Dr. Trew, Two remarkable Observations, which Animal Bodies suggest, 1st, That the same general Ends are accomplished in different Animals by all the possible Varieties of Means. 2dly, That Animal Bodies are Machines, which produce in themselves all those Changes, that are necessary for their Preservation and Well-being. Thus the same general Ends of Chyli-fication, Circulation, Secretion of Bile, &c. are accomplished in different Animals by Organs that differ considerably from each other; and in the same Animal the Body of the Fetus is very different in its Structure from that of the Adult, at the same time that this Difference is effected by the Body itself, each subsequent Variation, the natural and mechanical Consequence of that which immediately preceded, and the Whole conducted in the best possible manner for the Welfare and Happiness of the Animal. The Author's Design in this Dissertation is to consider those Differences of a Human Body before and after Birth, which affect the Circulation of the Blood. And for this Purpose he has given us 78 very curious and accurate Figures of the Parts relating thereto, such as the Heart, and Trunks of the great Blood-vessels, the Liver, the Vena Portarum, the Umbilical Chord, &c. subjoining to them a very minute and precise Explanation of each. Some of these Figures represent the Parts as they appeared immediately upon Dissection, others as inflated and dried, others again as injected with Wax; and lastly, others as having been first injected, and well dried, then cleared of the Injection, and laid open, in order to shew the several Cavities and Valves in their natural Dimensions and Positions. This last Method he prefers to all the rest, and observes, with relation to it, that the Injection must not be thrown in too hot, and that the internal Parts of the Preparation must be perfectly dry before we attempt to evacuate it; inasmuch as a Neglect of either of these Cautions would make the Valves, and their Membranes, shrivel up and contract themselves from their natural Sizes and Positions. The Manner of doing it is to suspend the Preparation in a proper Vessel placed in a gentle Heat, having first made an Aperture in the most depending Part, for the Injection to run out at. From these Figures, with their Explanations, our Author draws the following Anatomical and Physiological Conclusions. 1st, That, contrary to Casserius's Figure, the Umbilical Vein enters the Liver towards the Left Part of it. 2dly, That the Sulcus of the Liver, through which the Umbilical Vein passes, is not always the same. In some Subjects it surrounds the Vein along its whole Passage, in others only in Part of its Passage, and in others it is an imperfect Chanel, which merely receives the Vein. 3dly, There is but one Umbilical Vein, it empties itself into the Left Extremity of the Sinus Vena Portarum, and sends no Branches to the Liver. 4thly, The Communication between the Umbilical Vein, and the Sinus Vena Portarum, is so free, that the Blood has no Obstacle in passing either Way. Our Author asks therefore, What is the Cause of the Blood's Motion from the Umbilical Vein into the Liver, and whether the Pulsation of the Umbilical Arteries be one sufficient to produce this Effect? 5thly, The Vena Portarum sends no Branches to the Liver, but opens into a particular Sinus, called Sinus Vena Portarum; and this Opening is nearer to the Right Extremity of the Sinus than to the Left. 6thly, The Diameter of the Vena Portarum is much less than that of the Umbilical Vein. The Diameter of the Left Part of the Sinus Vena Portarum is generally larger than both these together, never much less than that of the Umbilical Veins; and the Diameter of the Canalis Venosus is least of all. The Blood therefore of the Vena Portarum mixes with that of the Umbilical Vein in the Sinus. And since the Blood of the Umbilical Vein, which abounds with chylous Particles, does thus mix with that of the Vena Portarum in the Fetus, it may be asked, Whether in Adults the Branches of the Vena Portarum, which arise from the Stomach and Intestines, testines, do not suck up some chylous Parts from the Aliment? And whether both in the Fetus, and in the Adult, Chyle be not a necessary Ingredient in the Composition of Bile? It is certain, that the Chyle passes into the Vena Portarum in Birds. 7thly, The Canalis Venosus empties itself into the Cava Inferior, where the Three Veins arising from the Liver empty themselves. 8thly, The Valves which are placed at the Two Extremities of the Canalis Venosus, facilitate the Ascent of the Blood in it, and also contribute to close it after Birth. 9thly, The Valve of the Coronary Vein is nothing else but its external Coat, something elongated within the Cavity of the Right Auricle; and its Use is to close the Orifice of this Vein when the Auricle is distended with Blood, just as the nervous Coat of the Bladder closes the Orifices of the Ureters when the Bladder is distended with Urine. 10thly, Eustachius's Valve is found both in the Fetus, and in the Adult; and its Use seems to be, to direct the Blood's Motion variously, according to the various Circumstances of the Right Auricle, during its Diastole and Systole; and principally to hinder the Regress of the Blood into the Cava Inferior, when the Auricle is contracted. 11thly, The Use of the Foramen Ovale, and Canalis Arteriosus, seems to be, to intercept Part of the venal Blood, and transmit it to the Left Auricle and Aorta, that so the Whole be not forced upon the Lungs during their State of Inactivity in the Fetus; of the Membrane, which is placed before the Foramen Ovale, to direct the Communication of the Auricles Auricles before Birth, and prevent it afterwards; and lastly, of the valvulous Productions at the Two Extremities of the Canalis Arteriosus, in like manner to direct the Blood in its Motion through this Canal before Birth, and to exclude it afterwards. Here our Author enters into a very minute Examination of Monsieur Mery's Hypothesis, but does not agree to it; affirming, that the Membrane of the Foramen Ovale is so placed as to permit the Blood to pass freely from the Right Auricle to the Left, during the Diastole of the Auricles, but never from the Left Auricle to the Right. 12thly, The Use of the Urachus in the human Fœtus is not yet discovered. Our Author here supposes, according to the Determination of the best Anatomists, that the human Fœtus has no Allantois. 13thly, The Situation of the Stomach in the Fœtus is such, as makes up for the want of Action in the Diaphragm, as far as relates to Digestion. For as in the Adult, the Action of the Diaphragm facilitates the Descent of the Aliment, so in the Fœtus the Cardia is made to rise above the Pylorus more than in the Adult, from its Connexion with the Diaphragm, for the same Purpose. 14thly, The Smallness of the Stomach in new-born Children shews, that it ought not to be oppressed either with much Aliment at once, or with such as is gross. 15thly, The Descent of the Testicles into the Scrotum does not always happen at the same time. 16thly, The recurrent Nerve seems to be some way subservient to the Canalis Arteriosus. This our Author conjectures from its passing round the Aorta just just where this receives the Canalis Arteriosus; but observes, that the Knowledge of the Use and Action of the Nervous System is much more imperfect than any other Branch of the Animal Oeconomy. There is a short Dissertation (with Four Figures of the Tongue, its Vessels, Glands, Muscles, and Nerves annexed) by the same Author; whose principal Intent is to shew, that the Vessels called Salival Ducts by Coschwitzius, are not Salival Ducts, but Veins. VIII. Some curious Experiments and Observations on a Beetle, that lived Three Years without Food: Communicated to the Royal Society in a Letter from Mr. Henry Baker to Alexander Stuart, M.D. F.R.S. SIR, WHEN I had the Honour of waiting on you lately, and was mentioning, in Conversation, the uncommon and surprising Strength of Life bestowed by Providence on a certain English Insect, called by Petiver, Scarabaeus impennis tardipes, the slow-legged Beetle. Moff. 139. Fig. id. Angl. 999. Gaz. Decad. 3æ, Tab. xxiv. 7. (whose Natural History, as to that Particular, has never, I believe, been touched on) you was pleased to think it so extraordinary, as to desire I would write down the Observations I had made, since the Accidents that led me into them may perhaps never again occur: And you seemed of Opinion, that their being known may