Compare with Carbo anim & Crotalus hori in Female genitalia.

Female Genitalia: Carbo animalis vs Crotalus horridus
Homoeopathic Materia Medica comparison,

1. Source: Charcoal of animal tissue;Carbo animalis, ox-hide, leather, etc. Hahnemannian proving | Venom of the timber rattlesnake proving by Hering, Marcy, Allen (Crotalus horridus)
2. Sphincter / core theme: Sluggish venous congestion, glandular induration, burning, putridity, “carbonisation” of tissue (Carbo animalis)| Septicaemic, haemorrhagic diathesis, dark fluid blood that won’t coagulate, malignant break-down (Crotalus horridus)
3. Menses ;character: Premature; flow is too early, then exhaustion follows (1) (Carbo animalis)| Delayed, dark, scanty, often 6–8 week interval; very painful at start (2) (Crotalus horridus)
4. Menses; amount & quality: Premature catamenia; menses followed by great exhaustion (Carbo animalis) (1) | Menses dark and scant; or, in menopause, prolonged metrorrhagia, dark, fluid, offensive(3) (Crotalus horridus)
5. Dysmenorrhoea: Not a leading feature; more about exhaustion after menses (1) (Carbo animalis)| Menses “very painful at beginning” (2); pains extend down thighs with aching in region of heart (4) (Crotalus horridus)
6. Vicarious menstruation: Not a strong feature ;more glandular/leucorrhoeal (1) (Carbo animalis)| Vicarious menstruation in debilitated, depraved states (2,3) epistaxis, bleeding from other sites (Crotalus horridus)
7. Metrorrhagia / haemorrhage: Uterine haemorrhage “where there is much affection of the glands” (1) (Carbo animalis) slow, passive, glandular background | Malignant uterine bleeding, great tendency, blood dark, fluid, offensive(3); non-coagulating haemorrhage; flooding at menopause (3) (Crotalus horridus)
8. Leucorrhoea: Burning, smarting leucorrhoea; imparts a yellow tinge to the linen(1) corrosive, staining (Carbo animalis)| Leucorrhoea offensive, bloody (2); thin, foul (Crotalus horridus)
9. Lochia: Serous and fetid lochia (1) late, putrid, thin (Carbo animalis)| Lochia thin, offensive, bloody, prolonged ;part of the haemorrhagic / septic picture (2) (Crotalus horridus)
10. Uterus: Indurations and nodosities; glandular hardness; tendency to chronic engorgement, “carbonised” tissue (1) (Carbo animalis)| Inflammation of ovaries and uterus (5); malignant disease of uterus; putrid fevers; low form of metritis with flooding (3) (Crotalus horridus)
11. Ovaries: Not a chief focus; symptoms are more uterine/breast than ovarian (1) (Carbo animalis)| Inflammation of the ovaries (5); ovarian region sensitive, congestive (Crotalus horridus)
12. Vagina / vulva: Burning, smarting discharge; tissues feel weak, lax; itching not dominant (1) (Carbo animalis)| Smarting, burning; tendency to bleed from slightest touch; haemorrhagic oozing (3) (Crotalus horridus)
13. Mammae: Painful nodosities and indurations in the mammae; erysipelatous inflammation of breasts (1) a strong Carbo animalis keynote | Breast symptoms less central; mammae can be livid, blue, with haemorrhagic tendency (3) (Crotalus horridus)
14. Pregnancy: Nausea of pregnant women, worse at night; faint, empty sensation in stomach from nursing (1) (Carbo animalis)| Threatened abortion with dark fluid bleeding; haemorrhagic tendency in pregnancy (2) (Crotalus horridus)
15. Menopause: Not a special focus (1) (Carbo animalis)| Intense flushings and drenching perspirations; faintness and sinking at stomach; prolonged metrorrhagia, dark, fluid, offensive; profound anaemia (3) a leading Crotalus menopause picture (Crotalus horridus)
16. Modalities ;better / worse: Better from cold air (typical Carbo veg. tendency); worse from warmth, fatty foods, evening (1) (Carbo animalis)| Worse from warm drinks, alcohol, on falling asleep (the rattlesnake “cough”), on left side; better from cold air; hot, feverish states (3,5) (Crotalus horridus)
17. Concomitants: Weakness, faintness, glandular swelling, “burning in the chest” extending down, evening aggravation, flatulence, loathing of fat (1) (Carbo animalis)| Haemorrhagic diathesis, jaundice, dark bleeding from every orifice, drowsiness with inability to sleep, dyspnoea, loquacity / muttering delirium, paralysis (2,3,5) (Crotalus horridus)
18. Mental picture (overlap with genitalia): Sad, weeping, anxious about health; fears being alone (1) (Carbo animalis)| Loquacity stupor; muttering; dread of being alone when sick; aversion to family/society (5) (Crotalus horridus)

Key differentiating notes (the bedside comparison)

1. Type of bleeding is the opposite.
Carbo animalis: premature, scanty-lean flow with glandular induration and burning discharge, staining linen yellow, plus burning smarting leucorrhoea (1).
Crotalus horridus: delayed, dark, scanty menses in young women; but profuse dark fluid haemorrhage in menopause / malignancy. The blood is offensive, fluid, does not coagulate(2,3).

2. Mammae vs Uterus.
Carbo animalis has a strong breast focus (nodosities, indurations, erysipelatous mammae) Clarke lists this under “Female Sexual Organs” for a reason (1).
Crotalus rarely features mammae; its signature is the uterus bleeding + ovaries + menopause flooding (3,5).

3. Putridity direction.
Carbo animalis is “putrid but not bleeding” fetid lochia, serous and smelly, with glandular induration (1).
Crotalus is “putrid AND bleeding” offensive, bloody, dark, fluid, non-coagulating (2,3).

4. Miasm / depth.
Carbo animalis sits more in the psoric–sycotic band: sluggish glands, indurations, chronicity (1).
Crotalus is psoric–syphilitic–miasmatic collapse: haemorrhagic diathesis, malignancy, septicaemia, jaundice, low fevers (2,3,5).

5. Clinical “type” overlaps and differentials (classic material medica groupings):
For burning, yellow-staining leucorrhoea + glandular induration: Carbo animalis; differentials: Carbo veg., Hydrastis, Kreosotum (1).
For dark, fluid, offensive, non-coagulating uterine bleeding, especially at menopause, with vicarious menstruation and septic fever Crotalus horridus; differentials: Lachesis, Phosphorus, Secale cornuta, Bothrops, Elaps, Naja (2,3).
For painful menses “very painful at start” Crotalus is higher than Carbo animalis in the repertory (genitalia-female, menses, painful, beginning of menses) (2,4).

One-line summary
> Carbo animalis on the female genitalia reads like “sluggish, burning, gland-hardened tissues with yellow-staining discharge” (1), while Crotalus horridus reads like “a haemorrhagic collapse with dark, fluid, offensive blood that refuses to clot, especially around menopause and in malignant disease” (2,3).

References

1. Clarke JH. A Dictionary of Practical Materia Medica. Vol. 1, Carbo animalis. London: The Homoeopathic Publishing Company; 1900. Chapter 16, Female Sexual Organs. Available from: https://www.materiamedica.info/en/materia-medica/john-henry-clarke/carbo-animalis
2. Hering C. The Guiding Symptoms of Our Materia Medica. Vol. 4, Crotalus horridus. Philadelphia: American Homoeopathic Publishing Society; 1880. Chapter 5, Menses, and Chapter 24, Female Sexual Organs. Available from: http://www.homeoint.org/hering/c/crot-h-5.htm
3. Allen HC. Keynotes and Characteristics with Comparisons of Some of the Leading Remedies of the Materia Medica. 4th ed. Philadelphia: Boericke & Tafel; 1916. Crotalus horridus. Available from: https://www.materiamedica.info/en/materia-medica/henry-c-allen/crotalus-horridus
4. Boericke W. Pocket Manual of Homoeopathic Materia Medica. 9th ed. Philadelphia: Boericke & Runyon; 1927. Crotalus horridus.
5. Kent JT. Lectures on Homoeopathic Materia Medica. Philadelphia: Boericke & Tafel; 1905. Crotalus horridus. Available from: https://www.vithoulkas.com/learning-tools/materia-medica-kent/crotalus-horridus-kent/