N.B.—Any pressure exerted on the umbilical cord during the process of delivery gives rise to respiratory acts on the part of the fœtus. The presence of what Casper calls petechial ecchymoses beneath the pleuræ, upon the aorta, and even on the heart, are, as a rule, a proof that attempts at respiration have been made. These petechial ecchymoses are sometimes found on the same parts in the drowned. (See “[Drowning].”)
How is the Hydrostatic Lung Test performed?
and What are the Objections to its Use?
As this test was first used, it consisted in placing the lungs, with or without the heart, in water, and then noting whether they sank or floated. A glass vessel, eighteen inches high and twelve in diameter, half filled with distilled water at 60° F., should be used. In summer, water at the ordinary temperature of the room will answer the purpose. To this rough test pressure is now added; the lung, or portions of it, are greatly compressed in a linen cloth, and then thrown into water as before. If the lungs thus compressed float, respiration is held to have taken place; should they sink, the contrary is presumed.
Pressure is used for the following reason: The air generated by putrefaction, and which may cause the lungs to float, is removed by pressure, but no amount of pressure, short of entirely destroying the lung tissue, will remove that which is the result of respiration or inflation; and between these the medical expert must decide from collateral evidence.
In performing the test: (1) Try if the lungs will float with the heart and thymus gland attached to them. (2) If they will float without the heart, &c. (3) Try if portions will float with or without pressure.
The following are the Objections to this Test:
- 1. The lungs may sink as a result of disease.
- 2. Respiration, even in healthy lungs, may be so imperfect
- that they may sink.
- 3. Emphysema pulmonum neonatorum.
- 4. Putrefaction.
- 5. Artificial inflation.
1. That in consequence of disease the entire lungs, or portions of them, may sink, and yet respiration may have taken place. Disease of the lung may occur previously to birth or soon afterwards, but it is scarcely probable that the disease would attack every portion of the lung. Parts, doubtless, small in proportion to the diseased part, may yet have been sufficiently inflated to float. The presence of disease is also not difficult of detection.
2. That respiration, even in healthy lungs, may be so imperfect that they may sink. This objection can scarcely be considered valid against the general application of the test, for in these cases there is no known test by which respiration or its absence can be determined. They are, therefore, out of the pale of the test, as they are out of every other mode of investigation.
3. Emphysema pulmonum neonatorum.—Emphysema is generally the result of excessive dilatation of the air cells of the lung, rupture of the cell walls, and infiltration of the intra-lobular areola tissue. This condition may be brought about by: