=Signs of Death by Suffocation.=--The first effect of arrest to the passage of air into the lungs is the stagnation of blood in the capillaries of the lungs. Non-arterial blood then goes to the brain and consciousness is soon lost. The respiratory sensation is then arrested by the circulation of venous blood. The left side of the heart becomes emptied, and then weak; the right side full and engorged. The great venous trunks are also more or less full, and the abdominal viscera, liver, spleen, and kidneys congested. The arrest of the heart‘s action is a secondary effect; the right side is paralysed by being too full, the left by being empty. These signs may be said to be typical, or, rather, are to be expected in death due to suffocation, but it must be distinctly stated that they are not always present. The right side of the heart is not in all cases engorged with blood; and Christison warns medical men against expecting “strongly marked appearances in every case of death from suffocation.” The heart, moreover, continues to contract after the lungs have ceased to perform their duty. Death is thus due to apnœa--that is, death beginning at the lungs--and not to syncope. Death in some cases is from neuro-paralysis or nervous apoplexy. In death by shock, which in most cases is instantaneous, both sides of the heart are equally filled. Death, the result of disease, may present all the signs of death from suffocation, and no suspicion may be aroused as to the cause of death from the _post-mortem_ appearances, especially if putrefaction have set in. The following table is given as an aid to diagnosis in this form of death: Points to be noticed in forming a Diagnosis of Death by Suffocation 1. _The Blood._--There is _unusual fluidity_ of the blood found in death by suffocation, however produced. This condition is sometimes present in deaths due to certain diseases, fevers, &c., and in cases of narcotic poisoning. Even with the blood in this condition, the presence of coagula in the cavities of the heart is not infrequent. The colour of the blood is changed to a dark purple, but in suffocation by carbon monoxide it is red. 2. _Animal Heat._--In persons who have died from suffocation the animal heat is long retained. 3. _Cadaveric Rigidity._--Other things being equal, the _rigor mortis_ is as well marked in this kind as in other forms of death. 4. _The Lungs._--Hyperæmia of the lungs is rarely absent. In most cases both lungs are engorged in about equal proportions. Hypostasis--_post-mortem stains_--must not be mistaken for capillary engorgement. 5. _The Heart._--Engorgement of the right side of the heart, the left being empty, or nearly so. It is advisable always to examine the heart first, and then the lungs. The pulmonary artery is also much congested.